chapter twelve saturated hydrocarbons. chapter 12 | slide 2 of 64 saturated hydrocarbons cont’d ©...

Chapter TwelveChapter TwelveSaturated

Hydrocarbons

Chapter 12 | Slide 2 of 64

Saturated Hydrocarbons cont’d

© Bill Ross/CORBIS

CO 12.1


← Fig. 12.1 Sheer numbers is one reason why organic chemistry is a separate field of chemical study.



Organic Chemistry

• The study of compounds containing ___________.

C

C

C

C

C

CC

C

C

C

C

C

C

C

C

C

C

C

C

C

C

C

CC

There are many more organic compounds than inorganic compounds. Why?


Properties of Organic Compounds

Typical organic compounds,

• Contain _____________

• Have ____________bonds

• Have low ____________________________– The bigger the molecule, _______________________________

• Have low ______________________– The bigger the molecule, _______________________________

• Are _______________

• Are soluble in ______________________

• Have a ______________ than water


The Bonding of Carbon

• To understand the bonding patterns of carbon, we must review what we know about carbon– Does carbon tend to form ionic or covalent compounds?

• .

– How many valence electrons does carbon have?• .

– How many electrons does carbon need to have an octet of electrons in its valence shell?

• .


Filling the Octet

• Carbon’s octet is filled when:

– .


Chemical Bonding of Carbon

• Carbon bonds in a ___________:

• Wedges: ___________________.• Dashed lines: ________________

__________.

C


Learning Check

• Complete the structure by adding the correct number of hydrogen atoms. Identify the molecular shape around each of the carbon atoms.

• C-C-C

• C=C-C

• C=C=C


Learning Check

• Complete the structure by adding the correct number of hydrogen atoms. Identify the molecular shape around each of the carbon atoms.

C

C

C

C

C

CC

C

C

C

C

C

C

C

C

C

C

C

C

C

C

C

CC


Representations of Organic Compounds

• Chemical Formulas show:

• Expanded structural formulas show:

• Condensed structural formulas show:

• Line drawings:


Converting Between Structural, Condensed, and Line Formulas

CC

CC

C

H

HH

C H

H

HH

H

H

H


Learning Check

• Convert the following structural formulas to condensed structural formulas and line drawings.

C

C

C

H

H

H

HH

H

C C CC

H

H

H

HH

H

H

H

H

H

C C

C

C

C

H

HH

H

H

H

H H

H

H

C

C

C

CC

C C

H

H

H

H

H

H

H

H

H H

H

H


Learning Check

• Convert the following line drawings to condensed structural formulas and complete structural formulas


Saturated v. Unsaturated

• Saturated Organic Compounds– .

• Unsaturated Organic Compounds– .

• Which compounds on the previous learning checks represent saturated organic compounds? Unsaturated organic compounds?


Learning Check

• Which are saturated organic compounds, which are unsaturated organic compounds?


← Fig. 12.3 Molecular structures of (a) methane, (b) ethane, and (c) propane, the three simplest alkanes.


Fig. 12.4 Models of (a) pentane, (b) isopentane, and (c) neopentane.


Alkanes

• Saturated hydrocarbons– Contain only __________________________– .– All carbon-carbon bonds are ____________________

• Determine the chemical formulas for the alkanes containing 3, 5, 7, and 9 carbons (separately)

• What is the relationship between the number of carbons and the number of hydrogens in these alkanes?– .


Fig. 12.2 Terms for organic compounds.


• Alkanes with four or more carbons can be drawn and can exist in more than one configuration:

• Structural isomers –

– The properties of compounds depend on ____________________________________________

C4H10

Isomers


Table 12.1 Selected Physical Properties of C4 and C5 Alkanes.


Conformations of Alkanes

• Single bonds are not locked in place. There is rotation around single bonds. As a result, alkanes exist in different conformations.– Conformation:

– Different conformations of the same molecule have the same condensed structural formula

– Show some examples:


Conformations of the Same Molecule or Different Molecules?

H2C

H2C

CH

H2C

CH2

CH2

CH3

H2C

CH

CH2

CH2

CH2

H2C

H3C

H3C

H2C

CH

CH3

CH3H2C

H2C

CH3

CH2

CH3

H3C

H2C

CH

CH3

CH3

H3C

CH

CH2

CH3

CH3


What are the two isomers of C2H6O?

CH

HH C

H

HOH C

H

HHO C

H

HH

CH

HH C

H

OHH C

H

HH C

H

HHO


Structural Isomers

• How many structural isomers can you draw for hexane?


• The number of carbon atoms attached to a branched carbon are designated by:– Primary:– Secondary:– Tertiary: – Quaternary:


CH

HHR C

H

RHR C

R

RHR C

R

RRR

primary

(R represents a general alkyl group.)

secondary

tertiary quaternary


Naming Alkanes

• We will use the IUPAC system (International Union of Pure and Applied Chemistry).– In this system, we name both the ____________ and

any ___________________ on the chain• Parent chain:

• Substituents:

– Alkyl groups

– Halogen groups


Naming the Parent Chain

• Depends on the length of the chain– 1 carbon: __________: CH3

– 2 carbons: _________ : CH3CH3

– 3 carbons: _________ : CH3CH2CH3

– 4 carbons: _________ : CH3CH2CH2CH3

– 5 carbons: _________ : CH3CH2CH2CH2CH3

– 6 carbons: _________ : CH3CH2CH2CH2CH2CH3

– 7 carbons: _________ : CH3CH2CH2CH2CH2CH2CH3

– 8 carbons: _________ : CH3CH2CH2CH2CH2CH2CH2CH3

– 9 carbons: _________ : CH3CH2CH2CH2CH2CH2CH2CH2CH3

– 10 carbons: _________ : CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3


Learning Check

A. What is the condensed formula for:

H H H H

H C C C C H

H H H H

B. What is its molecular formula?C. What is its name?


• Step 1:– Find the longest continuous carbon chain: The

longest chain is the parent.

CH3CH2CCH2CH3

CH2CH3

CH3CH2CH2CHCH3


• Step 2:– Number the carbon atoms in the main chain

beginning at the end near the first branch point.

CH3CH2CCH2CH3

CH2CH3

CH3CH2CH2CHCH3


Alkane Name Alkyl Group Name

CH4 Methane CH3 Methyl

CH3CH3 Ethane CH2CH3 Ethyl

CH3CH2CH3 Propane CH2CH2CH3

CH3CHCH3

Propyl

Isopropyl

• Step 3:– Identify and number the substituents.– Alkyl groups: occur when a hydrogen atom is

removed from an alkane. Replace “ane” with “yl”.


Fig. 12.5 The four most common branched-chain alkyl groups and their IUPAC names.

Naming Substituents


• Step 3:– Identify and number the substituents.– Use di, tri, tetra to name two like groups in an organic

molecule.

CH3CH2CCH2CH3

CH2CH3

CH3CH2CH2CHCH3


• Step 4:– Name the alkane as one word.

• Note: if two or more side chains, write in alphabetical order.

CH3CH2CCH2CH3

CH2CH3

CH3CH2CH2CHCH3


• Step 4:– Name the alkane as one word.

• Note: if two or more side chains, write in alphabetical order.

CH3CH2CCH2CH3

CH2CH3

CH3CH2CH2CHCH3

12

3

4567

Parts:heptane 3,3-diethyl4-methyl


Naming Conventions

• Carbons are numbered so the substituents get _____________________________

• Substituents are named ________________• Numbers are separated from each other by

_______________• Numbers are separated from letters by

__________________• There are _____________ in the name


Name this alkane.

CH3CH2CH2C CHCH3

CH3

• Longest chain?• Number the chain.• Substituents?• Name the alkane.


Name this alkane.

CH3CHCH2CCH3

CH2CH2CH3

CH3

• Longest chain?• Number the chain.• Substituents?• Name the alkane

CH3


Name this alkane.

CH3CH2CHCH2CHCH3

CH2CH3

CH3

• Longest chain?• Number the chain.• Substituents?• Name the alkane


Name this alkane.

CH3CH2CH2CH2C CHCH2CH3

CH2CH3

CH3

CH2CH3

• Longest chain?• Number the chain.• Substituents?• Name the Alkane


Draw the alkane.

• 2-methylheptane

• 4-ethyl-3,4-dimethyloctane


Draw the alkane.

• 2,3-dimethylhexane

• 4-ethyl-2,4-dimethylhexane


Cycloalkanes

• Saturated hydrocarbons in which ______________ _________________________________________

• Draw the structural formulas for the cycloalkanes with 4, 6, and 8 carbons.

• What is the relationship between the number of carbons and the number of hydrogens in a cycloalkane?– .


Cycloalkanes

• Properties:– .

cyclopropane cyclobutane cyclopentane cyclohexane


Fig. 12.6 Simple cycloalkanes


• Naming:– Count the carbons and add the prefix __________– For substituted cycloalkanes, start at point of

attachment and number around the ring to give any other substituent the ____________________.

– _______________________ has priority.

CH2CH3

CH3


CH2CH2CH3

CH3

Name this compound.


Learning Check


Isomerism in Cycloalkanes

• Cis-trans isomers:– Isomers that have the same molecular and structural

formulas but different ______________ ________________________________________ ________________________________________

• Cis isomer:

• Trans isomer:


H3C

H

H

H

CH3

H

H3C

H

H

CH3

H

H

cis (same) trans (opposite)

trans-1,2-dimethylcyclopropane cis-1,2-dimethylcyclopropane

Can also draw as:


Learning Check

• Determine whether cis-trans isomerism is possible for each of the following cycloalkanes. If so, then draw structural formulas for the cis and trans isomers– A. 1-ethyl-1-methylcyclopentane– B. Ethylcyclohexane– C. 1,4-dimethylcyclohexane– D. 1,1-dimethylcyclooctane


Chemical Reactions of Alkanes, I

• Combustion

In combustion reactions,

• Alkanes react with _____________.

• _________________________ are produced.

• Alkane + O2


Chemical Reactions of Alkanes, II

• Halogenation– .– In halogenation reactions,

– Requires _________________

– Reaction:


Figure 12.14 In an alkane substitution reaction, an incoming atom or group of atoms (represented by the orange sphere) replaces a hydrogen atom in

the alkane model.


An alkane in which one or more H atoms is replaced with a halogen (F, Cl, Br, or I)

CH3Br

Br

CH3CH2CHCH3

Cl

Haloalkanes


Name the following:Br

Cl

Cl

Learning Check


List other attached atoms or group ___________ ___________________

Br = bromo, Cl = chloro

Cl Br

CH3CHCH2CHCH2CH2CH3

Substituents


The name of this compound is:

Cl CH3

CH3CH2CHCH2CHCH3

1) 2,4-dimethylhexane

2) 3-chloro-5-methylhexane

3) 4-chloro-2-methylhexane

Learning Check


Table 12.4



Fig. 12.15 Models of four ethyl halides.



CAG 12.1

chapter twelve saturated hydrocarbons. chapter 12 | slide 2 of 64 saturated hydrocarbons cont’d ©...

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