Organic Chemistry Interactive Notes by jim.maxka@nau.edu Chapter 3: Functional Groups/Alkanes and Cycloalkanes

Other functional groups

Thiols R-SH (skunk and additive to natural gas) Nitro R-NO2 Others like imine, enamine, sulfonate, phosphonate.

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Identify Functional Groups: Taxol (anticancer).

NH

O

O

OO

O OO

O

O

OHO

O

CH3

OH

OH

CH3

CH3

CH3

CH3

CH3

Mifepristone (RU 486) Strychnine

CH3

O

OH

NCH3

CH3

CH3

NO

O

N

Tetradotoxin—puffer fish poison Erythrosine - Red #3

O

O

OH

OH

OHOH

NH

NH2+

NH

OH

OH

I

I

O O OH

I

IOH

O

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Alkanes: Relatively inert hydrocarbons Straight Chain Saturated Hydrocarbons Name Molecular

Formula Structural Formula

Number of Isomers

Boiling Point (oC)

Methane CH4 CH4 1 -161.0 Ethane C2H6 CH3CH3 1 -88.5 Propane C3H8 CH3CH2CH3 1 -42.0 Butane C4H10 CH3CH2CH2CH3 2 0.5 Pentane C5H12 CH3(CH2)3CH3 3 36.0 Hexane C6H14 CH3(CH2)4CH3 5 68.7 Heptane C7H16 CH3(CH2)5CH3 9 98.5 Octane C8H18 CH3(CH2)6CH3 18 125.6 Nonane C9H20 CH3(CH2)7CH3 35 150.7 Decane C10H22 CH3(CH2)8CH3 75 174.1 Undecane, Dodecane, …. Note these trends.

• The names are weird up to 4 and normal greek prefixes after. • The formulas and structures of these alkanes increase uniformly by CH2 • These formulas all fit the formula CnH2n+2 the highest possible H/C ratio • Since the H/C ratio in these compounds is at a maximum, we call them saturated.

Isomers result from different arrangements of molecular framework that are composed from the same molecular formula. For example, saturated arrangement of 4 carbons give two possible Lewis structures. Straight and branched.

CC

CCH

HH

H H

HH

H

H

H C

CC C

H

HH

H

HHH

H

H H

Draw these as condensed structures Draw these as line structure drawings. 5 carbons -- arranged in 3 possible ways -- straight, one branch and 2 branches.

CH3

CH2CH2

CH2CH3

CH3

CCH3 CH3

CH3CH3

CH2CH

CH3

CH3 Draw these as condensed structures

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Draw these as line structure drawings. Practice: Draw all five of the 6-carbon isomers. It helps if you name them. Alkyl Groups-Substituents

Name Formula Condensed Formula IUPAC Name Comments Methyl -CH3 CH3 * Methyl Methyl Ethyl -CH2CH3 CH2 *CH3 Ethyl 10

Propyl -CH2CH2CH3 CH2

*CH2CH3

Propyl 10

Isopropyl -CHCH(CH3)2 CH

*CH3

CH3

(1-methylethyl)- 20 Branched

Butyl -CH2CH2CH3 CH2

*CH2CH2

CH3

Butyl 10

Isobutyl -CH2CHCH(CH3)2 CH2

*CHCH3

CH3

(2-methylpropyl) 10 Branched

sec-butyl -CH(CH3)CH2CH3 CH

*CH2CH3

CH3

(1-methylpropyl) 20

tert-butyl -C(CH3)3 C *CH3

CH3

CH3

(1,1-Dimethylethyl) 30

Systematic Naming The IUPAC rules. Steps: • Find the longest chain.

Organic Chemistry Interactive Notes by jim.maxka@nau.edu • Groups attached to the parent chain are called substituents and are named based on the

number of carbons in the longest chain of that substituent, and are numbered using the number of the carbon atom on the parent chain to which they are attached.

• If the same substituent occurs more than once in a molecule, the number of each carbon of the parent chain where the substituent occurs is given and a multiplier is used to indicate the total number of identical substituents; i.e., dimethyl... trimethyl... tetraethyl..., etc.

• Numbering of the carbons in the parent chain is always done in the direction that gives the lowest number to the substituent which is encountered first, or, the lowest number at the first point of difference. If there are different substituents at equivalent positions on the chain, the substituent of lower alphabetical order is given the lowest number.

• In constructing the name, substituents are arranged in alphabetical order, without regard for multipliers.

• When these descriptors are used in an IUPAC name, iso is alphabetized normally; the hyphenated prefixes, however (sec- and tert-) are disregarded when alphabetizing.

• A more systematic method for the nomenclature of side-chains involves identifying the longest

chain in the substituent, numbering the substituent from the point of attachment to the parent, and indicating side-chains on the substituent using the standard method described for simple alkanes. The name is enclosed in parenthesis to indicate that the numbering corresponds to the local side-chain, not the parent chain. Thus:

• an isopropyl side-chain can also be named (1-methylethyl), • a sec-butyl side-chain can also be named (1-methylpropyl), • an isopentyl side-chain can also be named (3-methylbutyl), etc.

Organic Chemistry Interactive Notes by jim.maxka@nau.edu

• The origin of the prefixes sec- and tert-, given above, rests with an attempt to describe the nature of the branched carbon unit. By definition, a primary carbon is one which is attached to one other carbon atom, a secondary carbon is one which is attached to two, a tertiary carbon is attached to three, and a quaternary carbon is attached to four other carbon atoms; these are often abbreviated as 1 , 2 , 3 and 4 carbons.

Figures and much description above from http://chipo.chem.uic.edu/web1/ocol/SB/2-1.htm Practice: Name these C6H14 isomeric alkanes.

The Nitty Gritty Test yourself on this example

CH3 1 CH2

CH23 CH24

CH5 CH26

CH27 CH8

CH29 CH210

CH311

CH3

CHCH3

CH3

CH2CH3

-ethyl- -isopropyl- -methylundecane Now consider what is the best name.

CH3

CH2

CH3 CH24

CH25 CH6

CH2CH2

CH3

CH7CH3 CH28

CH39

CH2

CH3CH3 1

CH3

CH2

CH3 CH24

CH25 CH6

CH2CH2

CH3

CH7CH3 CH28

CH39

CH2

CH3CH3 1

Or -sec-butyl- -isopropylnonane -ethyl- , -dimethyl- -propylnonane

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Practice

CH3 CH

CH3

CH2 CH

CHCH3

CH3

CH2 C

CH3

CH3

CH2

CH2 CH2 CH3

CH3

CH2 CH2

CH2 C CH2

CH2 CH2

CH3

CH

CH2

CH3 CH2CH3

CH2

CH3

HC

CH3

CH3

isopropylcyclohexane or

CH3

CH3

CH3

Fine Points of Alphebetization CASE 1 alphebetizing with no IUPAC substituents 4-ethyl-3,3-dimethylhexane • Do not alphabetize di • Ethyl before methyl Draw: CASE 2 alphabetizing inside an IUPAC substituent 5-(1-ethyl-1,2-dimethylpropyl)nonane • Do not alphabetize di • Ethyl before methyl Draw: CASE 3 alphabetizing between IUPAC and simple substituents 3-(1,1-dimethylethyl)-4-ethylheptane • Alphabetize on di – it is the first letter of the IUPAC substituent Draw

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Petroleum Distillation A complete story of petroleum distillation can be read at the “How Stuff works” web site: http://science.howstuffworks.com/oil-refining4.htm Another good source written for chemical engineers can be found at. http://www1.cems.umn.edu/orgs/aiche/archive/history/h_refine.html

Which Fraction to Make? Various fractions are more important at different times of year. During the summer driving months, the public consumes vast amounts of gasoline, whereas during the winter more fuel oil is consumed. These demands also vary depending upon whether you live in the frigid north, or the humid south. Modern refineries are able to alter the ratios of the different fractions to meet demand, and maximize profit.

http://www1.cems.umn.edu/orgs/aiche/archive/history/h_refine.html

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Fractions Obtained from Crude Oils

Fraction Carbon chains

Boiling range (oC)

% of crude oil

Natural Gas C1 to C4 Below 20 10% Petroleum ether (solvent) C5 to C6 30 to 60 10% Naphtha (solvent) C7 to C8 60 to 90 10% Gasoline C6 to C12 75 to 200 40% Kerosene C12 to C15 200 to 300 10% Fuel oils, mineral oil C15 to C18 300 to 400 30% Lubricating oil, petroleum jelly, greases, paraffin wax, asphalt

C16 to C24 Over 400 10%

http://www.3rd1000.com/chptr10.htm The outcome of burning hydrocarbons. Hydrocarbons are burned for heat and gas expansion (ICE). Burning anything in the presence of oxygen is called . The general reaction looks like this: Complete combustion CxHy + O2 x CO2 + y/2 H2O + heat Assuming the hydrocarbon is octane, 15 gallons (avg tank of gas) burned completely in air makes about 350 lbs of CO2. 15 gal (3.8L/gal) (0.7kg/L) (1000g/kg) (1mole/114g) (8molesCO2/1moleC8H18) (44g/mole)(1kg/1000g)(2.2#/kg) = 270 lbs. Incomplete combustion: CxHy + O2 x CO + y/2 H2O + heat How do we deal with the CO? What is the reaction of burning coal? What are pollution problems from burning coal? What is the most desirable combustion reaction from an environmental point of view? What is the octane number? Some of the saturated hydrocarbons between C6 and C12 burn well and some don’t. In general, the straight chain hydrocarbons burn poorly with lots of soot. Increasing the branching of the hydrocarbons, increases the reactivity and makes the burning more efficient. On the octane scale:

CH2

CH2CH2CH3 CH2

CH2CH2

CH3

= 0 CH2

CHCCH3 CH3

CH3

CH3

CH3

= 100

The ICE needs high octane fuel to avoid afterburning or knocking. The diesel engine does best with poorer octane fuel because heat not a spark is what ignites the fuel. See http://auto.howstuffworks.com/diesel1.htm

Can you see the key to burning efficiency in organic structure? (VERY IMPORTANT for the course)

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Gas Chromatography Applications Gasoline The most common hydrocarbon analysis carried out by GC is probably that of gasoline. The analysis of gasoline is typical of the type of sample for which GC is the ideal technique. It is this type of multicomponent mixtures containing very similar compounds that need the high efficiencies available from GC for a successful analysis. The separation of a sample of gasoline carried out on a long open tubular column is shown in figure 35. It is clear that the column had a very high efficiency which was claimed to be in excess of 400,000 theoretical plates. The column was 100 m long and only 250 mm I.D., carrying a film of the stationary phase, Petrocol DH, 0.5 mm thick. Petrocol DH is specially designed stationary phase for the separation of hydrocarbons and consists of bonded dimethylsiloxane, a very dispersive type of stationary phase, retaining the solutes approximately in the order of their increasing boiling points.

1. Isobutane 12. 3–Methylhexane 23. o–Xylene 2. n–Butane 13. 2,3,4–Trimethylpentane 24. 1–Methyl–3–ethylbenzene 3. Isopentane 14. n–Heptane 25. 1,3,6–Trimethylbenzene 4. n–Pentane 15. 2,5–Dimethylhexane 26. 1,2,4–trimethylbenzene 5. 2,3–Dimethylbutane 16. 2,4–Dimethylhexane 27. 1,2,3–Trimethylbenzene 6. 2–Methylpentane 17. 2,3,4–Trimethylpentane 28 Naphthalene 7. 3–Methylpentane 18. Toluene 29. 2–Methylnaphthalene 8. n–Hexane 19. 2,3–Dimethylhexane 30. 1–Methylnaphthalene 9. 2,4–Dimethylpentane 20. Ethylbenzene 31. Dimethylnaphthalene 10. Benzene 21. m–Xylene 11. 2–Methylhexane 22. p–Xylene http://www.chromatography-online.org/Principles/Applications/Gas-Chromatography/Gasoline/rs70.html Courtesy of Supelco Inc.

Organic Chemistry Interactive Notes by jim.maxka@nau.edu

Cycloalkanes

Name Substituent Formula Condensed formula

Line formula Angles Strain

Cyclopropane Cyclopropyl C3H6

Cyclobutane Cyclobutyl C4H8

Cyclopentane Cyclopentyl C5H10

Cyclohexane Cyclohexyl C6H12

Cycloheptane Cycloheptyl

C7H14

Cycloalkane Cycloalkyl CnH2n

(CH2)n

Substituted cycloalkanes have 3 naming conventions that differ from alkanes.

1. If substituted, if the substituent is large or complicated then the cycloalkane can be named as a substituent.

2. The numbering starts at a substituted ring atom. 3. The numbering of more than one substituent will depend on picking the lowest possible

number combination for the substituents, with the lowest alphabetical substituent taking the lowest #. The direction may be clockwise or counterclockwise.

Examples of the IUPAC Rules in Practice http://www.cem.msu.edu/~reusch/VirtualText/nomen1.htm#start The following two cases provide examples of monosubstituted cycloalkanes.

More highly substituted cycloalkanes are named in a similar fashion, but care must be taken in numbering the ring.

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Cis-trans Since there can be no rotation around the sigma bonds in the ring, it is possible to have a new kind of isomer. This isomer has the same connectivity but different orientation in 3-D space. We indicate cis trans either with wedges and dashes or with a perspective-line projection technique. Consider 1,2-Dimethylcyclohexane

CH3

CH3H

CH3 CH3

H H

CH3 H

CH3CH3

CH3

CH3

CH3

cis -- same side

trans- opposite sidescis -- same side trans- opposite sides

H

CH3H

CH3

Unsaturation or HDI (Hydrogen Deficiency Index) CnH2n. Loss of hydrogen content is called unsaturation. Any time a ring is made, the structure loses 2 H’s. You also lose 2 h’s when you make a double bond. Formulas for saturated hydrocarbons are CnH2n+2. One unsaturation would give a formula CnH2n. Consider this example:

Propane CH3CH2CH3 Cyclopropane

CH2

CH2CH2 You can see the relationship between the two structures like this.

CH2

CH2CH2CH2

CH2

CH2

**

Use charts like these – if in doubt. For C6H6 C8H12 C7H12 Formula HDI Formula HDI Formula HDI C6H14 0 C8H18 0 C7H16 0 C6H12 1 C8H16 1 C7H14 1 C6H10 2 C8H15 2 C7H12 2 C6H8 3 C8H12 3 C6H6 4 Examples: Draw all of the isomers of C5H10 (no alkenes).

Organic Chemistry Interactive Notes by jim.maxka@nau.edu Draw all of the cis-trans isomers of Dimethylcyclopropane Dimethylcyclobutane Dimethylcyclopentane Summaries

1. Continue to review functional groups. Use flash cards. 2. Be able to identify functional groups. 3. Memorize the simple alkane names. Use flashcards. 4. Understand trends in physical properties of simple alkanes. 5. Know how to draw and recognize condensed structures. 6. Know how to draw and recognize line structures. 7. Know how to go in between line, condensed and Lewis structures. 8. Find the longest chain of an alkane. 9. Identify the substituents. 10. Construct a name with proper prefix numbers and alphabetical order. 11. Be able to name an alkane with common and IUPAC substituents. 12. Be able to draw alkanes from names. 13. Identify 1º, 2º, 3º, 4º carbons in an organic molecule. 14. Know how to draw all the isomers from a formula. 15. Know how to analyze a combustion reaction. 16. Know how to calculate degrees of unsaturation or HDI. 17. Know how to draw cycloalkanes from names. 18. Know how to name cycloalkanes from structures. 19. Be able to recognize cis/trans from cycloalkanes. 20. Be able draw cis and trans structures of cycloalkanes from names.