Brown, LeMay Ch 25AP Chemistry

Monta Vista High School

Problem Set: #5, 7, 9, 10, 11, 15, 20, 23 (not c), 41(not c), 44;Recommended: #2, 16, 17, 43, 69

25.1: Organic ChemistryThe study of carbon compounds, but not

limited to living systemsBiochemistry: study of the chemistry of living

things

Hydrocarbons are Compounds composed of only C and H

Combust to form CO2 and H2O Hydrocarbons have a

-parent carbon chain: It is the longest continuous carbon chain (does not have to be straight)- and a side substituent: Ex: alkyl groups 2

25.2: Intro to HydrocarbonsTypes:1. Alkanes: contain only single C-C bonds.

General formula Cn H2n+2, ending -ane Also called saturated (contain the maximum # of

H’s) Ex. Methane, Ethane etc.

Unsaturated: contain < maximum # of H’s2. Alkenes: contain at least one C=C bond.

General Formula CnH2n, ending - ene3. Alkynes: contain at least one C≡C bond.

General Formula CnH2n-2, ending - yne4. Aromatics: C’s connected in a planar ring

(contain and bonds) and have delocalization. Contain benzene ring, ex: benzene, chlorobenzene

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Organic Nomenclature

Originally formulated by IUPAC in 1892(http://www.acdlabs.com/iupac/nomenclature/)

1. Find the longest continuous chain of C atoms; use the name of this chain as the base of the compound’s name. This is called the parent carbon chain.1 = meth- 2 = eth- 3 = prop- 4 = but- 5 = pent-6 = hex- 7 = hept- 8 = oct- 9 = non- 10 = dec-

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prefix base suffix

What substituents?How many carbons in longest

chain?

What “family”?

2. Number the C atoms in the longest chain, beginning with the end nearest to a substituent. If different substituents are present, give the lowest number to the substituent with highest priority (see list on the website). The idea is to number the parent carbon chain to give the side substituents the lowest numbering.Priority List: carboxylic acid> aldehyde> ketone>alcohol> double or triple bond> alkyl grouphttp://www.chem.ucalgary.ca/courses/351/orgnom/functional/func.html

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3. Name and give the location (carbon #) of each substituent as prefixes or suffixes. (It varies.)

4. When 2 or more substituents are present, name them in alphabetical order as prefixes

When 2 or more of the same substituents are present, use a Greek prefix (di-, tri-, tetra-, penta-, hexa-, …)

Examples:

Saturated hydrocarbonsAlkanes: CnH2n+2; suffix is -ane

Cycloalkanes: CnH2n (n>2); prefix is cyclo-C’s bonded in a ring; not planar like an aromatic

compound (except cyclopropane)Ex: Draw Lewis structures of the first 4

cycloalkanes and name them.

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cyclopropanecyclobutane cyclohexane

Ways to represent Organic Compounds

Molecular Formula Ex: C4H10

condensed formula Ex:

H3C–CH2–CH2–CH3 or CH3CH2CH2CH3

CH3CH2CH2CH3

Structural formula Ex:

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Understanding CheckDraw condensed formula and structural

formula for the following: C3H8

Ex: Name all the molecules.CH4 C2H6

C3H8

C4H10

C5H12

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methane ethane

propane

butane

2-methylpropane

2,2-dimethylpropane

pentane

2-methylbutane

Write the name of the following:

______________________ ______________________

______________________ ______________________

______________________ ______________________

_______________________ ______________________

Draw condensed structural formulas for the following hydrocarbons:•2,3-dimethylpentane

•2,4-dimethylhexane

•Cyclohexane

•2,2-dimethylpropane

•2,4-dimethyl-1-hexene

•2,4,6-trinitromethylbenzene

•cis-2,3-dichloro-2-butene

•1,1,2-trichloroethane

•1,2-methylcyclohexane

•1,4-dichlorobenzene

•1-chloro-2-butyne

•1,3-cyclohexadiene

25.4 – 25.5: Functional GroupsNotation:“R” stands for:

Alkyl group, such as -CH3

-C2H5

-C3H7, etc. H

Carbonyls: contain a C=O

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Name of group

Formula of group

Suffix Name

Example structure

Example chemical

name

Carboxylic acid

O ||

R-C-OH

or

“R-COOH”

-oic acid

Ester

O ||

R-C-O-R

or

“R-COOR”

-yl ___oate

methanoic acid

ethyl propanoate

propyl ethanoate

Aldehyde

O

||

R-C-H

or

“R-CHO”

-al

KetoneO

||

R-C-R

-one

Alcohol

R-O-H

or

“R-OH”

-ol (suffix if highest priority)

hydroxyl- (prefix if

lower priority)

2-methyl- butanal

2-butanone

2,3-pentadiol

Ether R-C-O-C-R ___ ether

Amine R-NH2 -amineNH2

NH2

diethyl ether

2,2-pentadiamine

Alkene \ / C=C / \

-ene

Alkyne R-C≡C-R -yne

Halide R-X

halo-

(bromo-, chloro-, fluoro-, iodo-)

1-propene

2-butyne

2-bromopropane

Cycloalkene

C ring with

double bond(s)

cyclo-___-ene

Cycloalkane C ringcyclo-

___-ane

Alkane-(CH2)n-

CH3

-yl(as

functional group) or

-ane

cycloheptane

1-cyclopentene

2,3-dimethylbutane

Isomers:Compounds with same molecular formula but different

structures (different bonding arrangements)There are two main types of isomers:1. Structural Isomers: Same formula but differ in the

arrangement of atoms around the carbon chain. Structural isomers can be:

a. branched chain (depending on C chain)b. positional (position of a side group)c. functional group isomers (position of a functional

group). 2. Stereoisomers: Same formula but different 3-D

orientation. They can be of two types: a. Geometric Isomers ( cis, trans, double bonded C

atoms only) b. Optical Isomers (3D- orientation different-

chirality)21

Ex: Draw all the structural isomers for...CH4 C2H6

C3H8

C4H10

C5H12

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25.4: Geometric Isomers (cis-trans)Alkenes: CnH2n; prefix is bond #; suffix is –

ene(more than one double bond: –diene, -triene)

Geometrical isomers: same formula & same groups, but different structures.

cis- groups with highest priority on same side ofbond axis (high priority = high atomic

mass)trans- groups with highest priority diagonal/across

thedouble bond

Ex: Draw and name all the isomers of C4H8.

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x

y

x

y

The essential requirement for this stereoisomerism is that each carbon of the double bond must have two different substituent groups (one may be hydrogen). This is illustrated by the following general formulas. In the first example, the left-hand double bond carbon has two identical substituents (A) so stereoisomerism about the double bond is not possible (reversing substituents on the right-hand carbon gives the same configuration). In the next two examples, each double bond carbon atom has two different substituent groups and stereoisomerism exists, regardless of whether the two substituents on one carbon are the same as those on the other.Credits: http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/sterisom.htm

Credit: Google Images

Two molecules are optical isomers if they are non super imposable, mirror images of each other.http://www.wellesley.edu/Chemistry/Flick/chem341/opticalisomers.html

*25.7: ChiralityChiral: a molecule having a

nonsuperimposable mirror image(Originally discovered by Louis Pasteur)Compounds containing C atoms with four

different substituents are inherently chiral

Optical isomers or enantiomers: nonsuperimposable mirror images Labeled “L” (levo, left-handed) and “D” (dextro,

right-handed)Racemic: a mixture containing both

enantiomers (both L and D)

26http://nobelprize.org/educational_games/chemistry/chiral/

Alkynes: CnH2n-2; prefix is bond #; suffix is–yneReactions: unsaturated molecules are more

chemically reactive than saturated compounds

Addition: H3C-C≡C-CH3 + Br2 → ?

Hydrogenation:CH3-CH=CH-CH3 + H2 → ?

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Br―Br

→ H3C-C=C-CH3|Br

|Br

H―H→ H3C-CH―CH-CH3|

H|H

Aromatics: named like alkanes, but primarily based on benzenePrefix describes relative positions of

substituents:ortho- 2 substituents next to each othermeta- 2 substituents separated by one Cpara- 2 substituents separated by two C’s

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ortho- meta- para-

Naphthalene: “mothballs”