Prerequisites: 112

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CHEM 333
Prerequisites 112
synthesis
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CHAPTER 4 Nomenclature Conformation
of Alkanes Cycloalkanes Alkanes
Cycloalkanes Shapes IUPAC - R-H, R-X,
R-OH alkenes, cycloalkanes
alkenes, cycloalkenes alkynes Physical
properties Sigma bonds (s), rotations Conformation
of butane Ring strain - cycloalkanes Cyclohexane
conformation chair, boat, axial, equatorial,
substituted Bicyclic, fused alkanes Chemical rx
of alkanes Synthesis of alkanes
cycloalkanes Index of Hydrogen deficiency
3
CHAPTER 4 Nomenclature Conformation of
Alkanes Cycloalkanes
Alkanes Cycloalkanes Shapes IUPAC - R-H, R-X,
R-OH, alkenes, cycloalkenes, alkynes Sigma bonds
(s), rotations Conformation of butane Ring strain
- cycloalkanes Cyclohexane conformation chair,
boat, axial, equatorial, substituted cyclohexanes
Bicyclic, fused alkanes Lack of Chemical rxs of
alkanes Synthesis of alkanes cycloalkanes Index
of Hydrogen deficiency
4
Alkanes Cycloalkanes
Recall
Alkanes cycloalkanes are saturated
hydrocarbons(CH) All carbon-carbon (CC) bonds
are single bonds
Hydrocarbons that contain C-C Alkenes
(unsaturated hydrocarbon) Hydrocarbons that
contain CC Alkynes (unsaturated hydrocarbon)
Ch. 4 - 4
5
alkanes CnH2n2
cycloalkanes CnH2n
All carbon atoms in alkanes cycloalkanes - sp3
hybridized tetrahedral geometry
Ch. 4 - 5
6
Branched-chain alkanes
butane and methylpropane
same molecular formula (C4H10)
different bond connectivities constitutional
isomers
Ch. 4 - 6
7
C4 higher alkanes exist as constitutional
isomers
Molecular Formula of Possible Const. Isomers Molecular Formula of Possible Const. Isomers
C4H10 2 C9H20 35
C5H12 3 C10H22 75
C6H14 5 C20H42 366,319
C7H16 9 C40H82 62,481,801,147,341
C8H18 18
Ch. 4 - 7
8
constitutional isomers - different physical
properties
hexane Isomers (C6H14) hexane Isomers (C6H14) hexane Isomers (C6H14) hexane Isomers (C6H14)
Formula M.P.(oC) B.P.(oC)
-95 68.7
-153.7 60.3
-118 63.3
-128.8 58
-98 49.7
Ch. 4 - 8
9
More than 1 branch
International Union of Pure and Applied Chemistry
- IUPAC nomenclature system
Fundamental Principle Each compound shall have a
unique name
Ch. 4 - 9
10
The ending for alkane and cycloalkanes ane
prefix alkane
prefix number of carbons linearly connected
one meth-
two eth-
three prop-
four but-
five pent-
also cycloalkane infix numbercarbons
connected in a ring
Ch. 4 - 10
11
Unbranched alkanes
Name Structure Name Structure
methane CH4 hexane CH3(CH2)4CH3
ethane CH3CH3 heptane CH3(CH2)5CH3
propane CH3CH2CH3 octane CH3(CH2)6CH3
butane CH3CH2CH2CH3 nonane CH3(CH2)7CH3
pentane CH3(CH2)3CH3 decane CH3(CH2)8CH3
Ch. 4 - 11
12
Alkyl group - substituent or branch
Ch. 4 - 12
13
Nomenclature of Branched-Chain Alkanes
Rules 1. longest continuous carbon chain parent
chain
2. number chain form end to give substituent(s)
lowest possible number 3. number becomes the
substituent prefex
heptane
3-methyl
Ch. 4 - 13
14
4. For 2 or more substituents, use the lowest
possible individual numbers for parent
chain
6-ethyl-2-methyloctane
Substitutents listed alphabetically
Ch. 4 - 14
15
5. 2 substituents on the same carbon prefix w/
2 numbers
4-ethyl-4-methyloctane
6. Combine identical substituents - use di-,
tri-, tetra-, etc.
2,4-dimethylhexane
2,4,5-trimethylheptane
Ch. 4 - 15
16
7. With 2 or more chains of equal length select
the chain w/ greater number of substituents
2,3,5-trimethyl-4-propylheptane
Alphabetical order - disregard multiplying
prefix, di, tri etc. also number like sec-,
tert-
Ch. 4 - 16
17
8. Branching equal from either end Number from
the first (lowest) point of difference
NOT 2,4,5-
2,3,5-trimethylhexane
Ch. 4 - 17
18
Example 1
longest chain ?
3,4-dimethylheptane
Ch. 4 - 18
19
Use the lowest numbering for substituents
Substituents two methyl groups dimethyl
Ch. 4 - 19
20

• Example 1 (Contd)

• Complete name

Ch. 4 - 20
21
Example IUPAC name?
nonane
4-ethyl-3,7-dimethyl
Ch. 4 - 21
22
Example
nonane
7-ethyl-3-methyl-5-propylnonane
-ethyl- -methyl- -propylnonane
3-ethyl-7-methyl-5-propylnonane
23
Classification of Hydrogen Atoms
1o hydrogens (methyl group)
2o hydrogens (methylene gp)
3o hydrogens (methine gp)
Ch. 4 - 42
24

• Example 2 (Contd)

• Find the longest chain as parent

Ch. 4 - 22
25

• Example 2 (Contd)

• Find the longest chain as parent

? Nonane as parent
Ch. 4 - 23
26

• Example 2 (Contd)

• Use the lowest numbering for substituents

Ch. 4 - 24
27

• Example 2 (Contd)

• Substituents
• 3,7-dimethyl
• 4-ethyl

Ch. 4 - 25
28

• Example 2 (Contd)

• Substituents in alphabetical order
• Ethyl before dimethyl(recall Rule 4 disregard
  di)
• Complete name

Ch. 4 - 26
29
ring attach the prefix cyclo- to alkane -
cyclopropane
cyclopentane
Ch. 4 - 51
30
cycloalkanes - one substituent (C1)
methylcyclobutane
ethylcyclopropane
butylcyclopentane
Ch. 4 - 52
31
2 substituents - number from 1 to other (lowest
numbers)
1-ethyl-3-methylcyclopentane
Ch. 4 - 53
32
Cycloalkylalkanes as substituents ring with
less carbons than a chain becomes a substituent
cycloalkane
? cycloalkyl
1-cyclobutylpentane
Ch. 4 - 56
33
Bicyclic and Bridged Compounds not covered
Ch. 4 - 57
34
Nomenclature of Branched Alkyl Groups
For substituents w/ more than 2 carbons, more
than one substituent name might be
possible 3-carbons off of parent system
propylparent
ethyl..
1-methyl
or isopropyl..
Ch. 4 - 27
35
Four-carbons
1
1
3
butyl.....
propyl..... or isobutyl.....
2-methyl
3
1
1
2
1-methylpropyl..... or sec-butyl.....
1,1-dimethylethyl..... or tert-butyl.....
Ch. 4 - 28
36
cycloalkanes - one substituent (C1)
methylcyclobutane
methylethylcyclopropane
isopropylcyclopropane
tert-butylcyclopentane
dimethylethylcyclopentane
1-(1,1-dimethylethyl)cyclopentane
no numbers but if....
Ch. 4 - 52
37
5-carbons
Ch. 4 - 29
38
Example
nonane
5-tert-butyl-4-isopropylnonane
4-(methylethyl)-5-(dimethylethyl)nonane
Ch. 4 - 30
39
Example
5-sec-butyl-6-neopentyldecane
or 5-(1-methylpropyl)-6-(2,2-dimethylpropyl)decane
structure?
Ch. 4 - 36
40
Nomenclature of Alkyl Halides
Rules Halogens are always substituents (prefix)
F fluoro Br bromo Cl chloro I iodo
rules like alkyl substituents
Ch. 4 - 43
41
Halides (halo) always a substituent fluoro,
chloro, bromo, iodo
Example
(lowest numbers of substituents are 1,2,4 not
1,3,4)
Ch. 4 - 54
42

• Example 1 (Contd)

• Find the longest chain as parent

6-carbon chain
7-carbon chain
8-carbon chain
9-carbon chain
Ch. 4 - 31
43

• Example 1 (Contd)

• Find the longest chain as parent

? Nonane as parent
Ch. 4 - 32
44

• Example 1 (Contd)

• Use the lowest numbering for substituents

5,6
4,5 (lower numbering)
? Use 4,5
Ch. 4 - 33
45

• Example 1 (Contd)

• Substituents
• Isopropyl
• tert-butyl

? 4-isopropyl and 5-tert-butyl
Ch. 4 - 34
46

• Example 1 (Contd)

• Alphabetical order of substituents
• tert-butyl before isopropyl
• Complete name

Ch. 4 - 35
47

• Example 2 (Contd)

• Find the longest chain as parent

8-carbon chain
9-carbon chain
? decane as parent
10-carbon chain
Ch. 4 - 37
48

• Example 2 (Contd)

Ch. 4 - 38
49

• Example 2 (Contd)

• Use the lowest numbering for substituents

5,6
5,6
? Determined using the next Rules
Ch. 4 - 39
50

• Example 2 (Contd)

• Substituents
• sec-butyl
• Neopentyl

Ch. 4 - 40
51

• Example 2 (Contd)

• Since sec-butyl takes precedence over neopentyl
• 5-sec-butyl and 6-neopentyl
• Complete name

Ch. 4 - 41
52
Examples
2-bromo-1-chlorobutane
1,4-dichloro-3-methylhexane
3-methoxypentane
2-methyl-2-nitropropane
Ch. 4 - 44
53
IUPAC Nomenclature of Alcohols
numbers, prefixes, parent compound, and suffixes
Rules 1. Select the longest continuous chain
containing the hydroxyl group.
2. Change final e to suffix ol
3. Number the longest chain so OH gp has the
lower number.
4. Numbers locate OH group and substituent(s)
hexanol
4-methyl-1-
Ch. 4 - 45
54
Example 3
The carbon bearing the OH gets the lowest number.
Ch. 4 - 55
55
2-propanol
1,2,3-butanetriol
2-heptanol
3-propyl-2-heptanol
6-chloro-3-propyl-2-heptanol
Ch. 4 - 46
56
Example
6-chloro-3-propyl-2-heptanol
Ch. 4 - 47
57

• Example 4 (Contd)

• Find the longest chain as parent

Longest chain but does not contain the OH group
7-carbon chain containing the OH group
? Heptane as parent
Ch. 4 - 48
58

• Example 4 (Contd)

• Use the lowest numbering for the carbon bearing
  the OH group

2,3 (lower numbering)
5,6
? Use 2,3
Ch. 4 - 49
59

• Example 4 (Contd)

• Parent and suffix
• 2-Heptanol

• Substituents
• Propyl

• Complete name
• 3-Propyl-2-heptanol

Ch. 4 - 50
60
Example (Contd)
Between the two bridgeheads Two-carbon bridge on
the left Two-carbon bridge on the
right One-carbon bridge in the middle
Complete name bicyclo2.2.1heptane
Ch. 4 - 58
61

• Other examples

Ch. 4 - 59
62
Nomenclature of Alkenes Cycloalkenes
Rule 1. The longest chain w/ CC is the parent
name change the ending ane to ene
2. Number so the CC bond has the lowest number.
3. Use the first atom of CC as the prefix.
Locant/number of the CC precedes the parent
name OR placed immediately before the
suffix
4. Locate the substituents by the CC numbers
Ch. 4 - 60
63
Examples
Ch. 4 - 61
64
5. Cycloalkenes, CC bond assigned 1 2 Ring
numbered so substituents have lower numbers at
the first point of difference
3,5-dimethyl-1-cyclohexene
Not 4,6-dimethyl-1-
Ch. 4 - 62
65
6. Compounds w/ a CC OH alkenols (or
cycloalkenols) Give the OH carbon the lower
number
6-ethoxy-2-methyl-2-cyclohexen-1-ol
Ch. 4 - 63
66
Examples
Ch. 4 - 64
67
Alkynes - named like alkenes, but sufix is yne
2-heptyne
Ch. 4 - 69
68
7. Vinyl group allyl group
ethenylcyclopropane cyclopropylethene (or
vinylcyclopropane)
3-(prop-2-en-1-yl)cyclohexan-1-ol (or
3-allylcyclohexanol)
Ch. 4 - 65
69
Example - IUPAC name
4-tert-butyl-2-methyl-1-heptene
Ch. 4 - 66
70
8. cis and trans isomers same molecular
weight same connectivity different distribution
in space
cis 2 identical/substantial gps on the same side
of CC
cis-1,2-dichloroethene
trans-1,2-dichloroethene
trans 2 identical gps on opposite side of CC
Ch. 4 - 67
71
8. cis and trans isomers same molecular
weight same connectivity different distribution
in space
cis-1,2-dichloroethene
trans-1,2-dichloroethene
Note no rotation about double bonds
Ch. 4 - 68
72
Alkynes - named like alkenes, but sufix is yne
2-heptyne
OH group has priority over ene and yne
2-methyl-5-octyn-2-ol
Ch. 4 - 69
73
OH group has priority over ene and yne
2-bromo-3-methyl-4-nitro -5-(1-propen-2-yl)-7-decy
n-1-ol
Ch. 4 - 70
74
2 groups on single bond can rotate Conformations
temporary molecular shapes from some rotation
about a single bond Conformer each possible
structure of a conformation Conformational
analysis analysis of energy changes occur as a
molecule undergoes rotations
Ch. 4 - 71
75
Newman Projections
staggered conformation
Ch. 4 - 72
76
eclipsed conformation
Ch. 4 - 73
77
Newman Projections
Staggered conformation
Ch. 4 - 74
78
eclipsed conformation
Ch. 4 - 75
79
Ch. 4 - 76
80
Ch. 4 - 77
81
Ch. 4 - 78
82
eclipsed
gauche
anti
Ch. 4 - 79
83
Ring strain comprises Angle strain Torsional
strain
deviation from ideal bond angles (109.5o)
restricted rotation forces eclipsed, skewed vs
anti conformations
Ch. 4 - 80
84
Cyclopropane
Internal bond angle (?) 60o (49.5o deviated
from tetrahedral angle)
Ch. 4 - 81
85
Cyclobutane - ring is slightly folded
Internal bond angle (?) 88o (21o deviated from
109.5o)
If planar
angle strain decreased but torsional strain
considerably larger all 8 CH bonds eclipsed
Ch. 4 - 82
86
Cyclopentane
planar cyclopentane 108o, sp3 109.5o
Ch. 4 - 83
87
Ch. 4 - 84
88
boat is higher energy than the chair due to
Ch. 4 - 85
89
twist boat conformation lower energy than
boat higher energy than chair
Ch. 4 - 86
90
Energy diagram
Ch. 4 - 87
91
equatorial hydrogens in chair form
equator
axial hydrogens
perpendicular to ring
Ch. 4 - 88
92
substituted cyclohexane - flip between chairs
Ch. 4 - 89
93
Axial-G conformation has 1,3-diaxial interaction
The larger G the greater the 1,3-diaxial
interaction
Equilibrium shifts toward the chair w/
G-equatorial
Ch. 4 - 90
94
At 25oC At 25oC At 25oC
G of Equatorial of Axial
F 60 40
CH3 95 5
iPr 97 3
tBu gt 99.99 lt 0.01
Ch. 4 - 91
95
trans-diaxial
trans-diequatorial
Ch. 4 - 92
96
Upper-lower bonds - groups are trans
Ch. 4 - 93
97
cis-1,4-dimethylcyclohexanes
equatorial-axial
axial-equatorial
but cis-1-tert-butyl-4-methylcyclohexane (groups
different size)
Ch. 4 - 94
98
trans-1,3-dimethylcyclohexane
same stability
Ch. 4 - 95
99
trans-1-tert-butyl-3-methylcyclohexane
more stable large group equatorial
less stable large group axial
Ch. 4 - 96
100
trans-1,2-dimethylcyclohexane
equal energy
Ch. 4 - 97
101
Ch. 4 - 98
102
C60 Buckminsterfullerene
Ch. 4 - 99
103
Hydrogenation of Alkenes Alkynes (addition)
Ch. 4 - 100
104
Examples
Ch. 4 - 101
105
(No Transcript)
106
Index of hydrogen deficiency (IHD)
Difference or Comparison number of pairs of
hydrogens of unknown compound to an acyclic
alkane w/ same number of carbons
C7H16
C7H10
Ch. 4 - 103
107
Index of hydrogen deficiency (IHD)
Saturated acyclic alkanes CnH2n2
Each double bond or ring 2 hydrogens
less CnH2n Each double bond or ring provides
one unit of hydrogen deficiency
3
2
IHD
4
Ch. 4 - 104
108
e.g. unknown C6H12
C6H12
one pair of Hs H2
Index of hydrogen deficiency (IHD) 1
spectroscopy and/or rxs
C6H12
Ch. 4 - 105
109
IHD ?
IHD ?
IHD ?
110
For compounds containing Halogen count halogen
atoms as though they were hydrogen atoms Oxygen
ignore oxygen atoms and calculate IHD from the
remainder of the formula Nitrogen subtract one
hydrogen for each nitrogen atom and ignore
nitrogen atoms
Ch. 4 - 107
111
Example IHD of C4H6Cl2 Count Cl as H C4H6Cl2 ?
C4H8 A C4 acyclic alkane C4H2(4)2 C4H10
C4H10
C4H8
H2
one pair of Hs 1
IHD of C4H6Cl2
Possible structures
Ch. 4 - 108
112
Example IHD of C5H8O Ignore oxygen C5H8O ?
C5H8 A C5 acyclic alkane C5H2(5)2 C5H12
C5H12
C5H8
H4
end
two pair of Hs 2
IHD of C5H8O
Possible structures
Ch. 4 - 109
113
Example IHD of C5H7N Subtract 1 H for each
N C5H7N ? C5H6 A C5 acyclic alkane C5H2(5)2
C5H12
C5H12
C5H6
H6
IHD of C5H7N
three pair of Hs 3
Possible structures
end - 110