Chapter 21 : Organic Chemistry Organic chemistry: Organic chemistry: The study of the compounds of...

Chapter 21 : Organic Chemistry

Organic chemistry:Organic chemistry:The study of the compounds of carbon.

• 85% of all known compounds are organic.

• Carbohydrates, lipids, proteins, enzymes, nucleic acids, hormones, vitamins, and almost all other chemicals in living systems are organic compounds.

< Abundance of the elements in the Earth’s crust.


Why is organic chemistry a separate discipline within chemistry?

OrganicOrganic InorganicInorganic

Vitalism:Vitalism: a “vital force” present in living organisms was believed to be necessary to produce an organic compound.

The experiment of Wöhler in 1828 was the first in a series of experiments that led to the demise of the vital force theory. See reaction below:

NH4Cl AgNCO H2N-C-NH2

OAgCl+ heat +

Ammoniumchloride

Silvercyanate

Urea Silverchloride


Structural formula:Structural formula: Shows the atoms present in a molecule as well as the bonds that connect them.VSEPR model:VSEPR model: The most common bond angles are 109.5°, 120°, and 180°.

180°

120°

109.5°

H


Hydrocarbon:Hydrocarbon: A compound composed only of carbon and hydrogen.

H-C C-HH-C-C-HH

H

H

H HC C

H

H H

Hydrocarbons

Alkanes(Chapter 11)

Alkenes(Chapter 12)

Alkynes(Chapter 12)

Arenes(Chapter 13)

Only carbon-carbon single

bonds

One or more carbon-carbondouble bonds

One or morecarbon-carbontriple bonds

One or morebenzene-like

rings

Ethane Ethene(Ethylene)

Ethyne(Acetylene)

Benzene

Alkanes Alkenes AlkynesArenes

(Aromatics)


Alkanes:Alkanes: Hydrocarbons that contain only carbon-carbon single bonds.

CH4 CH4C2H6 CH3CH3C3H8 CH3CH2CH3C4H10 CH3(CH2)2CH3C5H12 CH3(CH2)3CH3

C6H14 CH3(CH2)4CH3C7H16 CH3(CH2)5CH3C8H18 CH3(CH2)6CH3C9H20 CH3(CH2)7CH3C10H22 CH3(CH2)8CH3

CH4 CH4C2H6 CH3CH3C3H8 CH3CH2CH3C4H10 CH3(CH2)2CH3C5H12 CH3(CH2)3CH3

C6H14 CH3(CH2)4CH3C7H16 CH3(CH2)5CH3C8H18C9H20C10H22

CondensedStructural Formula

MolecularFormulaName

decane

nonane

octane

heptane

hexane

pentane

butane

propane

ethanemethane





decane

nonane

octane

heptane

hexane

pentane

butane

propane

ethanemethane

CondensedStructural FormulaName

The first 10 alkanes with unbranched chains:


Line-angle formulaLine-angle formula:1. A line represents a single bond.2. A vertex and a line terminus represent a carbon atom.3. Hydrogen atoms are not shown in line-angle formulas.

CH3CH2CH2CH3CH3CH2CH3 CH3CH2CH2CH2CH3CH3CH2CH2CH3CH3CH2CH3 CH3CH2CH2CH2CH3PentaneButanePropane PentaneButanePropane

Condensedstructural

formula

Line-angleformula

Ball-and-stick model


Alkyl group: Alkyl group: A substituent group derived from an alkane by removal A substituent group derived from an alkane by removal of a hydrogen atom.of a hydrogen atom.•Commonly represented by the symbol R-.Commonly represented by the symbol R-.•Named by dropping the -ane from the name of the parent alkane Named by dropping the -ane from the name of the parent alkane and adding the suffix -yl.and adding the suffix -yl.

-CH2CH3

-CH3

-CH2CH2CH3

-CHCH3CH3

-CH2CH2CH2CH3

-CH2CHCH3CH3

-CHCH2CH3CH3

-CCH3

CH3

CH3

tert-butyl

sec-butyl

isobutyl

butyl

isopropyl

propyl

ethyl

methylName


CondensedStructural FormulaName


IUPAC, How to name alkanes:IUPAC, How to name alkanes:1. The name for an alkane with an unbranched chain of carbon atoms consists of a prefix showing the number of carbon atoms and the ending -ane.ane.2. For branched-chain alkanes, the longest chain of carbon atoms is the parent chain and its name is the root name.3. Name and number each substituent on the parent chain and use a hyphen to connect the number to the name.4.Number the parent chain from the end that gives the lower number to the substituent encountered first.5.Indicate the number of times the substituent occurs by a prefix di-, tri-, tetra-, penta-, hexa-, and so forth.6.Use a comma to separate position numbers.7. Alphabetize the names of substituents first, and then insert these prefixes8.Do not include the prefixes di-, tri-, tetra- in alphabetizing.

CH3CHCH3

CH3

2-Methylpropane

12

3

CH2CH3

CH3CCH2CHCH2CH3

CH3

CH34-Ethyl-2,2-dimethylhexane

(not 2,2-dimethyl-4-ethylhexane)

23

45

61

IUPAC = International Union of Pure and Applied Chemistry


Cyclic hydrocarbonCyclic hydrocarbon: A hydrocarbon that contains carbon atoms : A hydrocarbon that contains carbon atoms joined to form a ring.joined to form a ring.Cycloalkane: Cycloalkane: A cyclic hydrocarbon in which all carbons of the ring A cyclic hydrocarbon in which all carbons of the ring are saturated (has only carbon-carbon single bonds).are saturated (has only carbon-carbon single bonds).Cycloalkanes with ring sizes of from 3 to over 30 carbon atoms are Cycloalkanes with ring sizes of from 3 to over 30 carbon atoms are found in nature.found in nature.Five-membered (cyclopentane) and six-membered (cyclohexane) Five-membered (cyclopentane) and six-membered (cyclohexane) rings are especially abundant in nature.rings are especially abundant in nature.

Cyclopentane Cyclohexane

Isopropylcyclopentane1-tert-Butyl-4-methylcyclohexane

1 4

Physical properties:Physical properties:1. Non-polar (they dissolve in other non-polar solvents!)2. Melting/Boiling points and Density:

CH4CH3CH3CH3CH2CH3CH3(CH2)2CH3

CH3(CH2)3CH3CH3(CH2)4CH3CH3(CH2)5CH3CH3(CH2)6CH3CH3(CH2)7CH3CH3(CH2)8CH3

methane

ethanepropane

butane

pentane

hexane

heptane

octanenonane

decane

Name

CondensedStructrualFormula

mp(°C)

bp(°C)

-182

-183

-190-138

-130

-95

-90

-57-51

-30

-164

-88

-420

36

69

98

126151

174

(a gas)

(a gas)

(a gas)(a gas)

0.626

0.659

0.684

0.7030.718

0.730

*For comparison, the density of H2O is 1 g/mL at 4°C.

Mol wt(amu)

16.0

30.144.1

58.1

72.2

86.2

100.2

114.2128.3142.3

Density of Liquid

(g/mL at 0° C)*


Natural gas• 90 to 95 percent methane. • 5 to 10 percent ethane, and • A mixture of other relatively

low-boiling alkanes.Petroleum• A thick, viscous liquid mixture of

thousands of compounds, most of them hydrocarbons formed from the decomposition of marine plants and animals.


An alcohol may be primary (1°), secondary (2°), or tertiary (3°).

CH3-C-OH

H

HCH3-C-OH

CH3

HCH3-C-OH

CH3

CH3

A 1° alcohol A 3° alcoholA 2° alcohol

Example: C3H8O


Example: C3H9N


Example: C4H8O


Example: C3H6O2

Chapter 21 : Organic Chemistry Organic chemistry: Organic chemistry: The study of the compounds of...

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