chapter 23: organic chemistry - university of texas...
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Chapter 23: Organic Chemistry Key topics: Nomenclature Functional groups Drawing skeletal structures Organic Chemistry o study of carbon-containing compounds o originally: compounds produced by living organisms o now: includes man-made compounds such as plastics
Why Carbon is Different electron configuration: [He]2s22p2 o effectively prohibits ion formation
(energetically VERY unfavorable to gain/lose 4 e–) o fills octet by sharing e–
Small atomic radius, n = 2 valence shell (no 2d orbitals) o short, strong bonds o good p orbital overlap to give π bonds o no 2d orbitals imparts stability (Si more reactive) o catenation to form chains and rings containing single,
double and triple bonds
Classes of Organic Compounds Variety comes from o carbon forming chains by bonding to itself o presence of elements other than C and H o Functional groups – a group of atoms that determines
many of a molecule’s properties o multiple bonds
Alkanes: • contain C atoms connected by single bonds, and H atoms connected to C with single bonds Low density; totally insoluble in water • Naming: 1. Identify the longest continuous C chain to get the
parent name (root + “ane”) 2. Number the C’s in the continuous chain, beginning at
the end closest to the substituent (branch point) 3. Identify the substituent and use a number and a prefix
to specify location and identity, respectively
# of Carbons Root name 1 Meth– 2 Eth– 3 Prop– 4 But– 5 Pent– 6 Hex– 7 Hept– 8 Oct– 9 Non–
10 Dec–
Name: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
3,3-dimethylhexane
C C
H
H
H
H
C
H
C
C
C
C
H
H
C
H
H
H
H
H
HHH
HHH
C C
H
H
H
H
C
H
C
C
C
C
H
H
C
H
H
H
H
H
HHH
HHH
• functional groups determine chemistry that compound will undergo (electrostatic maps shown below)
Alcohols: • contains –OH group (hydroxyl group) Methanol, ethanol, and propyl alcohol are miscible with water • naming: 1. Identify the longest chain that includes the –OH group
2. Change the –e ending to -ol 3. Number to give the –OH the lowest number 4. When the chain also contains an alkyl substituent, give
the –OH the lowest number
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Carboxylic Acids: • contains –COOH (carboxy) group polar; form strong hydrogen bonds with each other and water • naming:
1. Identify the longest chain that includes the carboxyl group
2. Change the –e ending to –oic acid 3. Number starting with the carbonyl (C=O) carbon 4. Use numbers and prefixes to indicate the position and
identity of any substituents
Esters: • contain –COO– group (between two other non-H groups) polar but cannot form strong hydrogen bonds • naming: -- Name as derivative of carboxylic acid by replacing the
–ic acid ending with –ate -- 1st part of name specifies the substituent that replaces the ionizable hydrogen of the corresponding acid Aldehydes: • contains –COH (carbonyl group) – at end of chain polar but cannot form strong hydrogen bonds with each other; however can form strong hydrogen bonds with water. • naming: 1. Identify the longest chain that includes the carbonyl
group 2. Change the –e ending to -al
3. Number starting with the carbonyl (C=O) carbon 4. Use numbers and prefixes to indicate the position and
identity of any substituents
Ketones: • contains –CO– (carbonyl group) -- between two other groups polar but cannot form strong hydrogen bonds with each other; however can form strong hydrogen bonds with water. • naming:
1. Identify the longest chain that includes the carbonyl group
2. Change the –e ending to -one 3. Number to give the carbonyl group the lowest possible
number 4. Use numbers and prefixes to indicate the position and
identity of any substituents
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
CH3CH2 CH2
CCH3
O
CH3CH
CH2COH
OCH3
Primary Amines: • contains –NH2 group moderately polar; can form strong hydrogen bonds to each other and to water • naming:
1. Identify the longest chain that includes the –NH2 group 2. Change the –e ending to -amine 3. Number starting with the carbon to which the –NH2
group is bonded 4. Use numbers and prefixes to indicate the position and
identity of any substituents Primary Amides: • contains –CONH2 group (e.g. peptides) can form strong hydrogen bonds to each other; therefore amides have high melting and boiling points • naming:
1. Can be named as derivatives of carboxylic acids -- Or, by replacing the –e ending with –amide
Compounds with More than One Substituent: • Prefixes of di, tri, tetra, penta and so forth are used to
denote the number of substituents • Substituent names are alphabetized • Numbers are used to indicate position of the alphabetized
substituents • Prefixes are not counted when alphabetizing Representing Organic Molecules: • large numbers of ways to organize atoms in an organic
molecules: e.g. C5OHx
• Condensed structural formula (Condensed Structure): shows the same information as a structural formula but in condensed form
octane: C8H18 CH3(CH2)6CH3 molecular formula condensed structural formula
-- branches indicated using parentheses
2-methylheptane C8H18 CH3CH(CH3)(CH2)4CH3 Molecular formula condensed structural formula • Kekulé structures: similar to Lewis structure but without
showing lone pairs