hs 102 chemistry.ppt13.10 sep

7/31/2019 Hs 102 Chemistry.ppt13.10 Sep

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HS-102

1. Fundamentals in Organic chemistry


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Where we are in Science, Technology &

Education among world???

World's Best Universities: Top 400


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Organic chemistryis a sub discipline within chemistryinvolving the scientific study of the structure, properties,

composition, reactions, and preparation of carbon-basedcompounds, hydrocarbons, and their derivatives. Thesecompounds may contain any number of other elements,including hydrogen, nitrogen, oxygen, the halogens as wellas phosphorus, silicon and sulfur.

What is Organic chemistry?


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Organic chemistry and you

Your eyes are using an organic compound(retinal) convert visible light into nerve

impulses. Drugs,

Petrochemicals, food, explosives, paints

etc.


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Organic Chemistry and energy

One of the biggest problems that the world isfacing today is ENERGYCRISIS. As the priceof energy continues to rise we are lookingtowards renewable energy for cheaper sources

of power.

The readily available of these resources is TheSUN. For a long time scientists have beenworking on various devices to harvest solarenergy as it is the most essential component offuture energy resources.


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The most economical is Organic solar cell

The best way to ESCAPE from a problem is to SOLVE itAlan Saporta

A solar cell or photovoltaic cell is a

device that converts solar energy intoelectricity


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Generation Materials Performance Production Cost

First Single Crystal Si High High

SecondCdTe, CuInGaSe,

Amorphous SiMedium Medium

Third Organic Low Low

ClassificationSolar Cells are classified into three generations.

High

CHALLENGE!

Current power conversion efficiencies are

too low for commercial implementation

(especially at full solar intensities)


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Why Organic Solar Cells ?!

Much less expensive organic dyes

Much less expensive to fabricate

Organic source never exhausted

Flexible plastic film solar cells Lightweight weight solar cells

Diversity of organic materials

Easy purification of organic dyes


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Device Structure

Low Cost Process!

(Solution-Process, Roll-To-Roll)

Low Temperature Process!

Simple Structure!

Ubiquitous & Mobile Power Systems!Add Value to Existing Products!

Abundant Material Choice!

Low Toxicity!


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Mechanism of photovoltaic conversionprocess


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Light Absorption (Material Design)

Matching the solar emission spectrum

Charge Generation

(Material Design)

Efficient photoinduced charge transfer

Charge Transport and Collection at Electrodes

(Structure & Contacts Designs) Better charge carrier mobility


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Device Materials for Organic Solar Cell

Donor Materials

(p-type organic semiconductors)


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Acceptor Materials

(n-type organic semiconductors)

C &


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Current Trends: Advantages &

Drawbacks

Advantages: The most successful organic solar materialsystem uses fullerene derivative, PCBM as an electronacceptor and a conducting polymer, P3HT, as an electrondonor. Efficiencies of these bulk hetero junction solar cellshave been reported to be around 5%.

Drawbacks: The solubility ofPCBM is a limiting factor and it

is also cost effective. Therefore extensive research isrequired to synthesize more effective acceptor materials.


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Our Approach

To synthesize highly efficient and durable

Fullerene derivative which is applicable for

organic photovoltaic solar cell.

To synthesize highly soluble materials for

photovoltaic cell.

Synthesis of monomers for polymerization


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17

EWG= CO2Me, CO2Et, -CN, NO2 Pentafluoro, -SO2CF3, etc

Electron-withdrawing group willincrease acceptability of electrons

Electron-donating group attached tocyclopropane will raise LUMO level

(R) Long alkyl chains

will increase solubility

EWG OR

OR

Our Research


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HS 102 ChemistryMid semester Exam

(24th-30th October 2010)

UNIT 1: Fundamentals of Organic Chemistry:

1). Modern concept of Bonding, (sp3, sp2, sp hybridization)

2). Organic Reactions (Addition, Elimination and substitution

rearrangement reactions. 3). Fundamentals of reaction mechanism.

UNIT 2:

1). Chemistry of Benzene, conjugation and aromaticity.

2). Stereoisomerism, structural representation of stereo-isomers.

3). Optical and geometrical isomers.


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UNIT 3: Instrumental Analysis 1). Spectroscopy (NMR, IR, UV, Visible). 2) Chromatographic Techniques.

UNIT 4: Cements

1). Introduction, Manufacture of Portland cement,chemical composition of Portland cement, chemicalconstituents of Portland

2.) Setting and hardening of cement, heat of

hydration, special cement.

** Each Unit 3 Lectures.


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Structure of molecules

UNIT 1: Fundamentals of Organic Chemistry:


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Hybridization of atomic orbitals, sp3


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Sp2 Hybridization


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Fundamentals of Reaction Mechanism


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Organic reactions

All organic molecules have an outer layer of many electrons, which occupy filledorbitals, bonding and nonbonding. Chargecharge repulsion between theseelectrons ensures that all molecules repel each other. Reaction will occur only ifthe molecules are given enough energy (the activation energy for the reaction)

for the molecules to pass the repulsion and get close enough to each other.


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Charge attraction brings molecules together

Electron flow is the key to reactivity


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Orbital overlap controls angle of

successful attack


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Chemistry Of Benzene


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Conjugation

j t d t i i h i t t
http://en.wikipedia.org/wiki/Conjugated_systemhttp://en.wikipedia.org/wiki/Conjugated_system


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conjugated system, in organic chemistry, a systemof atoms covalently bonded with alternating singleand multiple bonds.
http://en.wikipedia.org/wiki/Conjugated_systemhttp://en.wikipedia.org/wiki/Conjugated_system


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l li i


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Delocalization


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Isomerism

The compounds have the samemolecular formula but differ from

each other in physical or chemicalproperties, are called isomers andphenomenon is called isomerism..

Two main type of Isomerism:


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yp 1). Structural Isomerism: Same molecular formula but

different structural formula. a). Chain Isomerism b). Position Isomerism c). Funtional Isomerim d). Metamerism e). Tautomeris 2). Stereoisomerism: The stereoisomers have same structural

formula but differ in arrangement of atoms in space.Stereoisomerism is of two types.

a). Optical Isomerism b). Geometrical Isomerism


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StereochemistryENANTIOMERS AND CHIRAL MOLECULES

1. A chiral molecule is one that is not identical with its mirror

image.

2. Objects (and molecules) that are superposable on their

mirror images are achiral.

ENANTIOMERS AND CHIRAL MOLECULES


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1. A chiral molecule is one that is not identical with its

mirror image.

2. Objects (and molecules) that are superposable ontheir mirror images are achiral.

The mirror image of Left and right a left

hand is aright hand. hands are not

superposable


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The specific rotation depends on the temperature and wavelength oflight that is employed,Na D-line: 589.6 nm = 5896 , Temperature (T).

The magnitude of rotation is dependent on the solvent whensolutions are measured.

The direction of rotation of plane-polarized light is often incorporatedinto the names of optically active compounds


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A racemic mixture is a mixture of two enantiomers inequal proportions.

Many chiral molecules are present in


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Many chiral molecules are present in

nature as single enantiomers

PROPERTIES OF ENANTIOMERS: OPTICAL ACTIVITY


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1. Enantiomers have identical physical properties such asboiling points, melting

points, refractive indices, and solubilities in common solventsexcept optical

rotations.

1) Many of these properties are dependent on the magnitude

of the intermolecular forces operating between the molecules, and for molecules

that are mirror

images of each other these forces will be identical.

2) Enantiomers have identical infrared spectra, ultravioletspectra, and NMR

spectra if they are measured in achiral solvents.

3) Enantiomers have identical reaction rates with achiral

reagents.


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2. Enantiomers show different behavior only when theyinteract with other chiral

substances. 1) Enantiomers show different rates of reaction toward other

chiral molecules.

2) Enantiomers show different solubilities in chiral solvents

that consist of a single enantiomer or an excess of a single enantiomer.

3. Enantiomers rotate the plane ofplane-polarized light inequal amounts but in

opposite directions. 1) Separate enantiomers are said to be optically active

compounds.

DIASTEREOMERS


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2. Diastereomers are stereoisomers that are not mirrorimages of each other.

DIASTEREOMERS

1. Molecules have more than one stereogenic (chiral)center: diastereomers.


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Diastereoisomers are stereoisomers that are not enantiomers.

Diastereoisomers can be chiral or achiral.Diastereoisomers can arise when structures have more than one

stereogenic centre.


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FISCHER PROJECTION (Emil Fischer, 1891)


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( , )

h l d h


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Chiral compounds with no stereogenic centres


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CHIRAL DRUGS


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Ibuprofen (Advil, Motrin, Nuprin): an anti-inflammatory

agent

1) Only the (S) enantiomer is active.

2) The (R) enantiomer has no anti-inflammatory action.3) The (R) enantiomer is slowly converted to the (S)enantiomer in the body..

4) A medicine based on the (S) isomer is along takes

effect more quickly than the racemate.

GOAL


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GOAL

The preparation of enantiomerically pure drugs isone factor that makes enantioselective synthesisand the resolution of racemic drugs (separation intopure enantiomers) active areas of research today.


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3.In nucleophilic substitution reactions, the CX bond of the substrate

undergoesheterolysis, and the lone-pair electrons of the nucleophile

is used to form a newbond to the carbon atom:


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MOLECULAR REARRANGEMENTS


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The formation of the more stable alkene is the

general rule (Zaitsevs rule) in the acid-catalyzed


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general rule (Zaitsev s rule) in the acidcatalyzed

dehydration reactions of alcohols.

Cement


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A cement is a binder, a substance that sets and

hardens independently, and can bind othermaterials together. The word "cement" traces tothe Romans, who used the term opuscaementicium to describe masonry resemblingmodern concrete that was made from crushed rockwith burnt lime as binder. The volcanic ash andpulverized brick additives that were added to the

burnt lime to obtain a hydraulic binder were laterreferred to as cementum, cimentum, cment andcement.

The broadly used term lime connotes calcium-containing inorganic materials in which
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containing inorganic materials, in whichcarbonates, oxides and hydroxides of calcium,

silicon, magnesium, aluminum, & ironpredominate, such as limestone. By contrast,quicklime specifically applies to a single

chemical compound.

CaO (s) + H2O (l) Ca(OH)2(aq) (Hr= 63.7 kJ/mol of CaO)

Cement used in construction is characterized as

hydraulic or non-hydraulic
http://en.wikipedia.org/wiki/Limestonehttp://en.wikipedia.org/wiki/Limestone


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hydraulic ornon hydraulic

Hydraulic: Hydraulic cements (e.g. Portlandcement) harden because of hydrationchemical reactions that occur independently

of the admixture's water content; they canharden even underwater or when constantlyexposed to wet weather. The chemicalreaction that results when the anhydrouscement powder is mixed with water produceshydrates that are not water-soluble.

Non-hydraulic:Non-hydraulic cements (e.g.lime and gypsumplaster) must be kept dry
http://en.wikipedia.org/wiki/Gypsumhttp://en.wikipedia.org/wiki/Plasterhttp://en.wikipedia.org/wiki/Plasterhttp://en.wikipedia.org/wiki/Gypsum


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gyp p ) p yin order to retain its strength.

The most important use of cement is theproduction of mortar and concretethe

bonding of natural or artificial aggregates toform a strong building material that is durablein the face of normal environmental effects.
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Concrete should not be confused with

cement because the term cement refersonly to the anhydrous powder substance

(ground clinker) used to bind the

aggregate materials of concrete. Upon the

addition of water and/or additives the

cement mixture is referred to as concrete,

especially if aggregates have been added.
http://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Clinkerhttp://en.wikipedia.org/wiki/Clinkerhttp://en.wikipedia.org/wiki/Concrete


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Modern cement


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Modern hydraulic cements began to be developed

from the start of the Industrial Revolution (around

1800), driven by three main needs:

Hydraulic render(stucco) for finishing brickbuildings in wet climates.

Hydraulic mortars for masonry construction of

harbor works, etc ... , in contact with sea water.

Development of strong concretes.

Types of modern cement
http://en.wikipedia.org/wiki/Industrial_Revolutionhttp://en.wikipedia.org/wiki/Stuccohttp://en.wikipedia.org/wiki/Stuccohttp://en.wikipedia.org/wiki/Industrial_Revolution


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Cement is made by heating limestone (calcium

carbonate), with small quantities of other materials(such as clay) to 1450 C in a kiln, in a process knownas calcination, whereby a molecule ofcarbon dioxide isliberated from the calcium carbonate to form calciumoxide, or quicklime, which is then blended with the

other materials that have been included in the mix .The resulting hard substance, called 'clinker', is thenground with a small amount ofgypsum into a powderto make 'Ordinary Portland Cement', the mostcommonly used type of cement (often referred to as

OPC).
http://en.wikipedia.org/wiki/Limestonehttp://en.wikipedia.org/wiki/Clayhttp://en.wikipedia.org/wiki/Kilnhttp://en.wikipedia.org/wiki/Calcinationhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Calcium_oxidehttp://en.wikipedia.org/wiki/Calcium_oxidehttp://en.wikipedia.org/wiki/Gypsumhttp://en.wikipedia.org/wiki/Gypsumhttp://en.wikipedia.org/wiki/Gypsumhttp://en.wikipedia.org/wiki/Calcium_oxidehttp://en.wikipedia.org/wiki/Calcium_oxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Calcinationhttp://en.wikipedia.org/wiki/Kilnhttp://en.wikipedia.org/wiki/Clayhttp://en.wikipedia.org/wiki/Limestone


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Portland cement is a basic ingredient

ofconcrete, mortar and most non-speciality grout.The most common use for Portland cement is in theproduction of concrete. Concrete is a compositematerial consisting ofaggregate (gravel and sand),

cement, and water. As a construction material,concrete can be cast in almost any shape desired,and once hardened, can become a structural (loadbearing) element. Portland cement may be gray or

white.

Portland cement blends
http://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Mortar_(masonry)http://en.wikipedia.org/wiki/Grouthttp://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Gravelhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Sandhttp://en.wikipedia.org/wiki/Gravelhttp://en.wikipedia.org/wiki/Construction_aggregatehttp://en.wikipedia.org/wiki/Grouthttp://en.wikipedia.org/wiki/Mortar_(masonry)http://en.wikipedia.org/wiki/Concrete


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Portland blastfurnace cement contains up to70 % ground granulated blast furnace slag,with the rest Portland clinker and a littlegypsum. All compositions produce highultimate strength, but as slag content isincreased, early strength is reduced, whilesulfate resistance increases and heat evolution

diminishes. Used as an economic alternativeto Portland sulfate-resisting and low-heatcements.[8]

Portland flyash cementcontains up to 30 % flyash. The fly ash is pozzolanic, so that ultimate
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as e y as s po o a c, so t at u t atestrength is maintained. Because fly ash addition

allows a lower concrete water content, earlystrength can also be maintained. Where goodquality cheap fly ash is available, this can be an

economic alternative to ordinary Portland cement
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Portland pozzolan cement includes fly ashcement, since fly ash is a pozzolan, but alsoincludes cements made from other natural or

artificial pozzolans. In countrieswhere volcanic ashes are available(e.g. Italy, Chile, Mexico, the Philippines) thesecements are often the most common form inuse.

Portland silica fume cement. Addition ofsilicafume can yield exceptionally high strengths
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fume can yield exceptionally high strengths,and cements containing 5-20 % silica fume areoccasionally produced. However, silica fume ismore usually added to Portland cement at theconcrete mixer
http://en.wikipedia.org/wiki/Silica_fumehttp://en.wikipedia.org/wiki/Silica_fume


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Expansive cementscontain, in addition toPortland clinker, expansive clinkers (usuallysulfoaluminate clinkers), and are designed to

offset the effects of drying shrinkage that isnormally encountered with hydraulic cements.This allows large floor slabs (up to 60 msquare) to be prepared without contractionjoints.


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White blended cementsmay be made usingwhite clinker and white supplementary materialssuch as high-purity metakaolin.

Colored cementsare used for decorativepurposes. In some standards, the addition ofpigments to produce "colored Portland cement"is allowed. In other standards (e.g. ASTM),

pigments are not allowed constituents ofPortland cement, and colored cements are soldas "blended hydraulic cements".

Non-Portland hydraulic cements Pozzolan-lime cements Mixtures of ground pozzolan and lime are the cements
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Pozzolan-lime cements. Mixtures of ground pozzolan and lime are the cementsused by the Romans, and can be found in Roman structures still standing (e.g.the Pantheon in Rome). They develop strength slowly, but their ultimate strength

can be very high. The hydration products that produce strength are essentially thesame as those produced by Portland cement.

Slag-lime cements.Ground granulated blast furnace slag is not hydraulic on itsown, but is "activated" by addition of alkalis, most economically using lime. Theyare similar to pozzolan lime cements in their properties. Only granulated slag (i.e.water-quenched, glassy slag) is effective as a cement component.
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Calcium sulfoaluminate cements are made from clinkers thatinclude ye'elimite (Ca4(AlO2)6SO4 or C4A3 in Cement chemist'snotation) as a primary phase. They are used in expansive cements,in ultra-high early strength cements, and in "low-energy" cements.Hydration produces ettringite, and specialized physical properties(such as expansion or rapid reaction) are obtained by adjustment of

the availability of calcium and sulfate ions. Their use as a low-energy alternative to Portland cement has been pioneered in China,where several million tonnes per year are produced.[12][13] Energyrequirements are lower because of the lower kiln temperaturesrequired for reaction, and the lower amount of limestone (whichmust be endothermically decarbonated) in the mix. In addition, the

lower limestone content and lower fuel consumption leads to aCO2 emission around half that associated with Portland clinker.However, SO2 emissions are usually significantly higher.

"Natural" cementscorrespond to certain cements of the pre-
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p pPortland era, produced by burning argillaceous limestones at

moderate temperatures. The level of clay components in thelimestone (around 30-35 %) is such that large amountsofbelite (the low-early strength, high-late strength mineral inPortland cement) are formed without the formation ofexcessive amounts of free lime. As with any natural material,

such cements have highly variable properties.

Geopolymer cements are made from mixtures of water-soluble alkali metal silicates and aluminosilicate mineral

powders such as fly ashand metakaolin.

Supersulfated cements.These contain about 80% ground granulatedblast furnace slag 15 % gypsum or anhydrite and a little Portland clinker
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blast furnace slag, 15 % gypsum or anhydrite and a little Portland clinkeror lime as an activator. They produce strength by formation ofettringite,

with strength growth similar to a slow Portland cement. They exhibitgood resistance to aggressive agents, including sulfate.Calcium aluminate cements are hydraulic cements made primarilyfrom limestone and bauxite. The active ingredients are monocalcium

aluminate CaAl2O4 (CaO Al2O3 or CA in Cement chemist notation, CCN)and mayenite Ca12Al14O33 (12 CaO 7 Al2O3 , or C12A7 in CCN). Strengthforms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes,e.g. for furnace linings.

The hydration process: reactions
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In the anhydrous state, four main types of minerals arenormally present: alite, belite, aluminate (C3A) and a ferritephase (C4AF). For more information on the composition ofclinker, see the clinker pages. Also present are smallamounts of clinker sulfate (sulfates of sodium, potassiumand calcium) and also gypsum, which was added when theclinker was ground up to produce the familiar greypowder.When water is added, the reactions which occurare mostly exothermic, that is, the reactions generate heat.We can get an indication of the rate at which the mineralsare reacting by monitoring the rate at which heat is evolved

using a technique called conduction calorimetry. Anillustrative example of the heat evolution curve produced isshown below.


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Almost immediately on adding water some of the clinker sulphates and

gypsum dissolve producing an alkaline, sulfate-rich, solution.

Soon after mixing, the (C3A) phase (the most reactive of the four mainclinker minerals) reacts with the water to form an aluminate-rich gel(Stage I on the heat evolution curve above). The gel reacts with sulfate insolution to form small rod-like crystals of ettringite. (C3A) reaction is with

water is strongly exothermic but does not last long, typically only a fewminutes, and is followed by a period of a few hours of relatively low heatevolution. This is called the dormant, or induction period (Stage II).

The first part of the dormant period, up to perhaps half-way through,corresponds to when concrete can be placed. As the dormant period

progresses, the paste becomes too stiff to be workable.

The setting of cement


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Cement sets when mixed with water by way of acomplex series of hydration chemical reactionsstill only partly understood. The differentconstituents slowly hydrate and crystallise whilethe interlocking of their crystals gives to cementits strength.Carbon dioxide is slowly absorbed toconvert the portlandite (Ca(OH)2) intoinsoluble calcium carbonate. After the initialsetting, immersion in warmwater will speed up

setting. In Portland cement, gypsum is added as acompound preventing cement flash setting.

Environmental impactsC t f t i t l i t t
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Cement manufacture causes environmental impacts atall stages of the process. These include emissions of

airborne pollution in the form of dust, gases, noise andvibration when operating machinery and duringblasting in quarries, and damage to countryside fromquarrying. Equipment to reduce dust emissions duringquarrying and manufacture of cement is widely used,

and equipment to trap and separate exhaust gases arecoming into increased use. Environmental protectionalso includes the re-integration of quarries into thecountryside after they have been closed down byreturning them to nature or re-cultivating them

CO2 emissions
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Cement manufacturing releases CO2 in the atmosphere bothdirectly when calcium carbonate is heated,producing lime and carbon dioxide,[14] and also indirectly throughthe use of energy if its production involves the emission of CO2. Thecement industry is the second largest CO2 emitting industry behindpower generation. The cement industry produces about 5% of

global man-made CO2 emissions, ofwhich 50% is from the chemicalprocess, and 40% from burning fuel.[15] The amount of CO2 emittedby the cement industry is nearly 900 kg of CO2 for every 1000 kg ofcement produced.In certain applications, lime mortar, reabsorbs the CO2 chemicallyreleased in its manufacture, and has a lower energy requirement in

production. Newly developed cement types fromNovacem[17] and Eco-cement can absorb carbon dioxide fromambient air during hardening.

Heavy metal emissions in the air
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In some circumstances, mainly depending on the originand the composition of the raw materials used, thehigh-temperature calcination process of limestone andclay minerals can release in the atmosphere gases anddust rich in volatile heavy metals,a.o, thallium,[19]cadmium and mercury are the mosttoxic. Heavy metals (Tl, Cd, Hg, ...) are often found astraceelements in common metal sulfides (pyrite(FeS2), zinc blende (ZnS), galena (PbS), ...) present assecondary minerals in most of the raw materials.Environmental regulations exist in many countries to

limit these emissions.

Heavy metals present in the clinker
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The presence of heavy metals in the clinker arisesboth from the natural raw materials and from theuse of recycled by-products or alternative fuels.The high pH prevailing in the cement porewater(12.5 < pH < 13.5) limits the mobility of manyheavy metals by decreasing their solubility andincreasing their sorption onto the cement mineral

phases. Nickel, zinc and lead are commonly foundin cement in non-negligible concentrations.

Use of alternative fuels and by-productsmaterials
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A cement plant consumes 3 to 6 GJ of fuel per tonne of clinkerproduced, depending on the raw materials and the process used.Most cement kilns today use coal and petroleum coke as primaryfuels, and to a lesser extent natural gas and fuel oil. Selected wasteand by-products with recoverable calorific value can be used asfuels in a cement kiln, replacing a portion of conventional fossil

fuels, like coal, if they meet strict specifications. Selected waste andby-products containing useful minerals such as calcium, silica,alumina, and iron can be used as raw materials in the kiln, replacingraw materials such as clay, shale, and limestone. Because somematerials have both useful mineral content and recoverable calorificvalue, the distinction between alternative fuels and raw materials is

not always clear. For example, sewage sludge has a low butsignificant calorific value, and burns to give ash containing mineralsuseful in the clinker matrix

Cement industry in the world
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In 2002 the world production of hydrauliccement was 1,800 million metric tons. The topthree producers were China with 704, India

with 100, and the United States with 91million metric tons for a combined total ofabout half the world total by the world's threemost populated states

China


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"For the past 18 years, China consistently has produced more cement thanany other country in the world. [...] (However,) China's cement exportpeaked in 1994 with 11 million tons shipped out and has been in steadydecline ever since. Only 5.18 million tons were exported out of China in2002. Offered at $34 a ton, Chinese cement is pricing itself out of themarket as Thailand is asking as little as $20 for the same quality."[22]

In 2006 it was estimated that China manufactured 1.235 billion metric tonsof cement, which was 44% of the world total cementproduction.[23] "Demand for cement in China is expected to advance 5.4%annually and exceed 1 billion metric tons in 2008, driven by slowing buthealthy growth in construction expenditures. Cement consumed in China

will amount to 44% of global demand, and China will remain the world'slargest national consumer of cement by a large margin
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Benzene and its reaction with

electrophiles


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electrophiles

Benzene is a planar symmetrical hexagon withsix trigonal (sp2) carbon atoms, each havingone hydrogen atom in the plane of the ring.

All the bond lengths are 1.39 (compare CC1.47 and C=C 1.33 ). All the 13C shifts arethe same (dC 128.5 p.p.m.).

Electrophilic attack on benzene and

on cyclohexene


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on cyclohexene


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Mechanism for electrophilic aromaticsubstitution


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substitution


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Nitration of benzene


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Sulfonation of benzene


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Alkyl and acyl substituents can be added to a benzenering by the FriedelCrafts

reaction


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reaction


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Summary of electrophilic

substitution on benzene


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Phenols react rapidly with bromine


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Thin layer chromatography
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Thin layer chromatography (TLC) is

a chromatography technique used to separatemixtures. Thin layer chromatography is performed on asheet of glass, plastic, or aluminum foil, which is coatedwith a thin layer of adsorbent material, usually silicagel, aluminium oxide, or cellulose (blotter paper). This

layer of adsorbent is known as the stationary phase.After the sample has been applied on the plate,a solvent or solvent mixture (known as the mobilephase) is drawn up the plate via capillary action.Because different analytes ascend the TLC plate at

different rates, separation is achieved
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Thin layer chromatography can be used to: Monitor the progress of a reaction

Identify compounds present in a given

substance Determine the purity of a substance

Plate preparation

TLC plates are usually commercially available with


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TLC plates are usually commercially available, withstandard particle size ranges to improve reproducibility.

They are prepared by mixing the adsorbent, suchas silica gel, with a small amount ofinert binderlike calcium sulfate (gypsum) and water. This mixture isspread as a thick slurry on an unreactive carrier sheet,usually glass, thick aluminum foil, or plastic. Theresultant plate is dried and activatedby heating in anoven for thirty minutes at 110 C. The thickness of theadsorbent layer is typically around 0.1 0.25 mm foranalytical purposes and around 0.5 2.0 mm forpreparative TLC.
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Technique

TLC is often used for monitoring chemical reactions and for the qualitative analysis of reaction
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TLC is often used for monitoring chemical reactions and for the qualitative analysis of reactionproducts.

1. TLC is often used for monitoring chemical reactions and for the qualitative analysis of reactionproducts.

2. A small amount of an appropriate solvent (elutant) is poured in to a glass beaker or any othersuitable transparent container (separation chamber) to a depth of less than 1 centimeter. A stripof filter paper is put into the chamber, so that its bottom touches the solvent, and the paper lieson the chamber wall and reaches almost to the top of the container. The container is closed with acover glass or any other lid and is left for a few minutes to let the solvent vapors ascend the filterpaper and saturate the air in the chamber. (Failure to saturate the chamber will result in poorseparation and non-reproducible results).

3. The TLC plate is then placed in the chamber so that the spot(s) ofthe sample DO NOT TOUCHthe surface of the elutant in the chamber, and the lid is closed. The solvent moves up the plateby capillary action, meets the sample mixture and carries it up the plate (elutes the sample).When the solvent front reaches no higher than the top of the filter paper in the chamber, theplate should be removed (continuation of the elution will give a misleading result) and dried.

Different compounds in the sample mixture travel at differentrates due to the differences in their attraction to thestationary phase, and because of differences in solubility in
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the solvent. By changing the solvent, or perhaps using a

mixture, the separation of components (measured bythe Rfvalue) can be adjusted.

AnalysisIodine vapors are a general unspecific color reagent.

Specific color reagents exist into which the TLC plate is dipped or whichare sprayed onto the plate[6]Potassium permanganate - oxidation Iodine

The Rf

value , or retention factor, of each spot can bedetermined by dividing the distance traveled by the productby the total distance traveled by the solvent (the solventfront).

ApplicationsIn organic chemistry, reactions are qualitatively monitored with TLC.Spots sampled with a capillary tube are placed on the plate: a spot
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Spots sampled with a capillary tube are placed on the plate: a spotof starting material, a spot from the reaction mixture, and a "co-

spot" with both. A small (3 by 7 cm) TLC plate takes a couple ofminutes to run. The analysis is qualitative, and it will show if thestarting material has disappeared, i.e. the reaction is complete, ifany product has appeared, and how many products are generated(although this might be under-estimated due to co-elution).Unfortunately, TLCs from low-temperature reactions may give

misleading results, because the sample is warmed to roomtemperature in the capillary, which can alter the reactionthewarmed sample analyzed by TLC is not the same as what is in thelow-temperature flask. One such reaction is the DIBALH reductionof ester to aldehyde.

Column chromatography
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Column chromatography in chemistry is amethod used to purify individual chemicalcompounds from mixtures of compounds. It isoften used for preparative applications onscaleTwo methods are generally used to preparea column; the dry method, and the wet method.

For the dry method, the column is first filled withdry stationary phasepowder, followed by theaddition of mobile phase, which is flushed

through the column until it is completely wet,and from this point is never allowed to run dry.
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For the wet method, a slurry is prepared ofthe eluent with thestationary phase powder and thencarefully poured into the column. Care must be takento avoid air bubbles. A solution of the organic materialis pipetted on top of the stationary phase. This layer is

usually topped with a small layer of sand or with cottonor glass wool to protect the shape of the organic layerfrom the velocity of newly added eluent. Eluent isslowly passed through the column to advance theorganic material. Often a spherical eluent reservoir or

an eluent-filled and stoppered separating funnel is puton top of the column.
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The individual components are retained by thestationary phase differently and separate from eachother while they are running at different speedsthrough the column with the eluent. At the end of thecolumn they elute one at a time. During the entire

chromatography process the eluent is collected in aseries offractions. The composition of the eluent flowcan be monitored and each fraction is analyzed fordissolved compounds, e.g. by analyticalchromatography, UV absorption, orfluorescence.

Colored compounds (or fluorescent compounds withthe aid of an UV lamp) can be seen through the glasswall as moving bands.
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Stationary phaseThe stationary phase oradsorbentin column chromatography is a solid. The most commonstationary phase for column chromatography issilica gel, followed byalumina. Cellulose powderhas often been used in the past. Also possible are ion exchange chromatography, reversed-phase chromatography (RP), affinity chromatography or expanded bed adsorption (EBA). The

stationary phases are usually finely ground powders or gels and/or are microporous for anincreased surface, though in EBA a fluidized bed is used.

Mobile phase (eluent)

Th bil h l t i ith l t i t f
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The mobile phase or eluentis either a pure solvent or a mixture ofdifferent solvents. It is chosen so that the retention factor value of thecompound of interest is roughly around 0.2 - 0.3 in order to minimize thetime and the amount of eluent to run the chromatography. The eluent hasalso been chosen so that the different compounds can be separatedeffectively. The eluent is optimized in small scale pretests, often using thinlayer chromatography (TLC) with the same stationary phase.

A faster flow rate of the eluent minimizes the time required to run acolumn and thereby minimizes diffusion, resulting in a better separation,see Van Deemter's equation. A simple laboratory column runsby gravity flow. The flow rate of such a column can be increased byextending the fresh eluent filled column above the top of the stationary

phase or decreased by the tap controls. Better flow rates can be achievedby using a pump or by using compressed gas (e.g. air, nitrogen, or argon)to push the solvent through the column (flash columnchromatography).[1][2]
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The ultimate goal of chromatography is to separatedifferent components from a solution mixture. Theresolution expresses the extent of separation between thecomponents from the mixture. The higher the resolution ofthe chromatogram, the better the extent of separation ofthe samples the column gives. This data is a good way ofdetermining the columns separation properties of thatparticular sample. The resolution can be calculated fromthe chromatogram.The separate curves in the diagram represent differentsample elution concentration profiles over time based on

their affinity to the column resin. To calculate resolution,the retention time and curve width are required.


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The particle size of the stationary phase is generally finer inflash column chromatography than in gravity columnchromatography. For example, one of the most widely usedsilica gel grades in the former technique is mesh 230 400(40 63 m), while the latter technique typically requiresmesh 70 230 (63 200 m) silica gel.[3]

A spreadsheet that assists in the successful development offlash columns has been developed. The spreadsheetestimates the retention volume and band volume ofanalytes, the fraction numbers expected to contain eachanalyte, and the resolution between adjacent peaks. This

information allows users to select optimal parameters forpreparative-scale separations before the flash column itselfis attempted
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Gas chromatography

Gas chromatography (GC), is a common type
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ofchromatography used in analyticchemistryfor separating and analyzing compounds thatcan be vaporized without decomposition. Typical usesof GC include testing the purity of a particularsubstance, or separating the different components of a

mixture (the relative amounts of such components canalso be determined). In some situations, GC may helpin identifying a compound. In preparativechromatography, GC can be used to prepare pure

compounds from a mixture.

In gas chromatography, the moving phase (or "mobilephase") is a carrier gas, usually an inertgas suchas helium or an unreactive gas such as nitrogen
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as helium or an unreactive gas such as nitrogen.

The stationary phase is a microscopic layerofliquid orpolymer on an inert solid support, inside a pieceofglass or metaltubing called a column (a homage tothe fractionating column used in distillation). Theinstrument used to perform gas chromatography is called

a gas chromatograph (or "aerograph", "gas separator").The gaseous compounds being analyzed interact with thewalls of the column, which is coated with differentstationary phases. This causes each compound to elute at a

different time, known as the retention time of thecompound. The comparison of retention times is whatgives GC its analytical usefulness.

Gas chromatography is in principle similar to columnchromatography (as well as other forms ofchromatography, such as HPLC, TLC), but has severalnotable differences. Firstly, the process of separating
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notable differences. Firstly, the process of separating

the compounds in a mixture is carried out betweena liquid stationary phase and a gas moving phase,whereas in column chromatography the stationaryphase is a solid and the moving phase is a liquid.(Hence the full name of the procedure is "Gas-liquid

chromatography", referring to the mobile andstationary phases, respectively.) Secondly, thecolumn through which the gas phase passes islocated in an oven where the temperature of the gas

can be controlled, whereas column chromatography(typically) has no such temperature control. Thirdly,theconcentration of a compound in the gas phase issolely a function of the vapor pressure of the gas.

Gas chromatography is also similar to fractional distillation,since both processes separate the components of a mixture
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since both processes separate the components of a mixture

primarily based on boiling point (or vapor pressure)differences. However, fractional distillation is typically usedto separate components of a mixture on a large scale,whereas GC can be used on a much smaller scale (i.e.microscale).[1]

Gas chromatography is also sometimes known as vapor-phase chromatography (VPC), orgas-liquid partitionchromatography (GLPC). These alternative names, as wellas their respective abbreviations, are frequently foundin scientific literature. Strictly speaking, GLPC is the mostcorrect terminology, and is thus preferred by many authors.

GC analysisA gas chromatograph is a chemical analysis instrument for separating chemicals in a complexsample A gas chromatograph uses a flow through narrow tube known as the column
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sample. A gas chromatograph uses a flow-through narrow tube known as the column,through which different chemical constituents of a sample pass in a gas stream (carriergas,mobile phase) at different rates depending on their various chemical and physicalproperties and their interaction with a specific column filling, called the stationary phase. Asthe chemicals exit the end of the column, they are detected and identified electronically.The function of the stationary phase in the column is to separate different components,causing each one to exit the column at a different time (retention time). Other parametersthat can be used to alter the order or time of retention are the carrier gas flow rate, and thetemperature.

In a GC analysis, a known volume of gaseous or liquid analyte is injected into the "entrance"(head) of the column, usually using a microsyringe (or, solid phase microextraction fibers, ora gas source switching system). As the carrier gas sweeps the analyte molecules through thecolumn, this motion is inhibited by the adsorption of the analyte molecules either onto thecolumn walls or onto packing materials in the column. The rate at which the moleculesprogress along the column depends on the strength ofadsorption, which in turn depends onthe type of molecule and on the stationary phase materials. Since each type of molecule has

a different rate of progression, the various components of the analyte mixture are separatedas they progress along the column and reach the end of the column at different times(retention time). A detector is used to monitor the outlet stream from the column; thus, thetime at which each component reaches the outlet and the amount of that component canbe determined. Generally, substances are identified (qualitatively) by the order in which theyemerge (elute) from the column and by the retention time of the analyte in the column.

Physical components

The autosampler provides the means to introduce a sample automatically
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p p p yinto the inlets. Manual insertion of the sample is possible but is no longer

common. Automatic insertion provides better reproducibility and time-optimization.Different kinds of autosamplers exist. Autosamplers can be classified inrelation to sample capacity (auto-injectors vs. autosamplers, where auto-injectors can work a small number of samples), to robotic technologies (XYZrobot vs. rotating robot the most common), or to analysis:LiquidStatic head-space by syringe technologyDynamic head-space by transfer-line technology

Solid phase microextraction (SPME)

a complete range of autosamplers. Historically, the countries most active inautosampler technology development are the United States, Italy andSwitzerland.

Inlets

The column inlet (or injector) provides the means tod l fl f
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introduce a sample into a continuous flow of carriergas. The inlet is a piece of hardware attached tothe column head.

S/SL (Split/Splitless) injector; a sample is introduced into a heated small chamber via asyringe through a septum - the heat facilitatesvolatilization of the sample and sample matrix.The carrier gas then either sweeps the entirety (splitless mode) or a portion (splitmode) ofthe sample into the column. In split mode, a part of the sample/carrier gas mixture in theinjection chamber is exhausted through the split vent. Split injection is preferred whenworking with samples with high analyte concentrations (>0.1%) whereas splitless injection is

best suited for trace analysis with low amounts of analytes. (


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On-column inlet; the sample is here introduced in its entiretywithout heat.

Gas source inlet or gas switching valve; gaseous samples incollection bottles are connected to what is most commonly asix-portswitching valve. The carrier gas flow is not interruptedwhile a sample can be expanded into a previouslyevacuated sample loop. Upon switching, the contents of thesample loop are inserted into the carrier gas stream.

Columns Packed columns are 1.5 10 m in length and have an internal

diameter of 2 4 mm. The tubing is usually made of stainless steel
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or glass and contains apacking offinely divided, inert, solid support

material (e.g. diatomaceous earth) that is coated with a liquid orsolid stationary phase. The nature of the coating materialdetermines what type of materials will be most strongly adsorbed.Thus numerous columns are available that are designed to separatespecific types of compounds.

Capillary columns have a very small internal diameter, on the order

of a few tenths of millimeters, and lengths between 2560 metersare common. The inner column walls are coated with the activematerials (WCOT columns), some columns are quasi solid filled withmany parallel micropores (PLOT columns). Most capillary columnsare made of fused-silica (FSOT columns) with a polyimide outercoating. These columns are flexible, so a very long column can be

wound into a small coil.

Detectors

A number of detectors are used in gas
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chromatography. The most common arethe flame ionization detector (FID) andthe thermal conductivity detector (TCD). Bothare sensitive to a wide range of components,

and both work over a wide range ofconcentrations

Methods
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The method is the collection of conditions in which the GC operates

for a given analysis. Method development is the process ofdetermining what conditions are adequate and/or ideal for theanalysis required.

Conditions which can be varied to accommodate a required analysisinclude inlet temperature, detector temperature, columntemperature and temperature program, carrier gas and carrier gasflow rates, the column's stationary phase, diameter and length,inlet type and flow rates, sample size and injection technique.Depending on the detector(s) (see below) installed on the GC, theremay be a number of detector conditions that can also be varied.Some GCs also include valves which can change the route of sampleand carrier flow. The timing of the opening and closing of thesevalves can be important to method development.


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Carrier gas selection and flow rates


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Typical carrier gasesinclude helium, nitrogen, argon, hydrogen andair. Which gas to use is usually determined bythe detector being used, for example,a DID requires helium as the carrier gas.

Stationary compound selection
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The polarity of the solute is crucial for thechoice of stationary compound, which in anoptimal case would have a similar polaritythan the solute. Common stationary phases in

open tubular columns are cyanopropylphenyldimethyl polysiloxane, carbowaxpolyethyleneglycol, biscyanopropylcyanopropylphenyl polysiloxane and diphenyldimethyl polysiloxane. For packed columnsthere are more options available.

Application
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In general, substances that vaporize below ca. 300 C(and therefore are stable up to that temperature) canbe measured quantitatively. The samples are alsorequired to be salt-free; they should not contain ions.Very minute amounts of a substance can be measured,

but it is often required that the sample must bemeasured in comparison to a sample containing thepure, suspected substance.

Various temperature programs can be used to makethe readings more meaningful; for example to

differentiate between substances that behave similarlyduring the GC process.
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hs 102 chemistry.ppt13.10 sep

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