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Chapter 4 Alcohols and Alkyl Halides

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Title: Chapter 4 Alcohols and Alkyl Halides


1
Chapter 4Alcohols and Alkyl Halides
2
Overview of Chapter
This chapter introduces chemical reactions and
their mechanisms by focusing on two
reactionsthat yield alkyl halides.
  • (1) alcohol hydrogen halide
  • ROH HX ? RX H2O
  • (2) alkane halogen
  • RH X2 ? RX HX
  • Both are substitution reactions

3
4.1Functional Groups
4
Functional Group
  • a structural unit in a molecule responsible for
    itscharacteristic behavior under a particular
    set ofreaction conditions

5
Families of organic compoundsand their
functional groups
  • Alcohol ROH
  • Alkyl halide RX (X F, Cl, Br, I)
  • Amine primary amine RNH2
  • secondary amine R2NH
  • tertiary amine R3N

6
Families of organic compoundsand their
functional groups
Epoxide
  • Ether ROR'
  • Nitrile RCN
  • Nitroalkane RNO2
  • Sulfide RSR'
  • Thiol RSH

7
Many classes of organic compounds contain a
carbonyl group
R
Carbonyl group
Acyl group
8
Many classes of organic compounds contain a
carbonyl group
H
R
Carbonyl group
Aldehyde
9
Many classes of organic compounds contain a
carbonyl group
R'
R
Carbonyl group
Ketone
10
Many classes of organic compounds contain a
carbonyl group
OH
R
Carbonyl group
Carboxylic acid
11
Many classes of organic compounds contain a
carbonyl group
OR'
R
Ester
Carbonyl group
12
Many classes of organic compounds contain a
carbonyl group
NH2
R
Amide
Carbonyl group
13
4.2IUPAC Nomenclatureof Alkyl Halides
14
IUPAC Nomenclature
There are several kinds of IUPAC nomenclature.
  • The two that are most widely used
    are functional class nomenclature substitutive
    nomenclature
  • Both types can be applied to alcohols andalkyl
    halides.

15
Functional Class Nomenclature of Alkyl Halides
  • Name the alkyl group and the halogen asseparate
    words (alkyl halide)

CH3F
CH3CH2CH2CH2CH2Cl
16
Functional Class Nomenclature of Alkyl Halides
  • Name the alkyl group and the halogen asseparate
    words (alkyl halide)

CH3F
CH3CH2CH2CH2CH2Cl
Methyl fluoride
Pentyl chloride
1-Ethylbutyl bromide
Cyclohexyl iodide
17
Substitutive Nomenclature of Alkyl Halides
  • Name as halo-substituted alkanes.
  • Number the longest chain containing thehalogen
    in the direction that gives the lowestnumber to
    the substituted carbon.

CH3CH2CH2CH2CH2F
18
Substitutive Nomenclature of Alkyl Halides
  • Name as halo-substituted alkanes.
  • Number the longest chain containing thehalogen
    in the direction that gives the lowestnumber to
    the substituted carbon.

CH3CH2CH2CH2CH2F
1-Fluoropentane
2-Bromopentane
3-Iodopentane
19
Substitutive Nomenclature of Alkyl Halides
  • Halogen and alkyl groupsare of equal rank when
    it comes to numberingthe chain.
  • Number the chain in thedirection that gives the
    lowest number to thegroup (halogen or
    alkyl)that appears first.

20
Substitutive Nomenclature of Alkyl Halides
5-Chloro-2-methylheptane
2-Chloro-5-methylheptane
21
4.3IUPAC Nomenclatureof Alcohols
22
Functional Class Nomenclature of Alcohols
  • Name the alkyl group and add "alcohol" as
    aseparate word.

CH3CH2OH
23
Functional Class Nomenclature of Alcohols
  • Name the alkyl group and add "alcohol" as
    aseparate word.

CH3CH2OH
Ethyl alcohol
1,1-Dimethylbutylalcohol
1-Methylpentyl alcohol
24
Substitutive Nomenclature of Alcohols
  • Name as "alkanols." Replace -e ending of
    alkanename by -ol.
  • Number chain in direction that gives lowest
    numberto the carbon that bears the OH group.

CH3CH2OH
25
Substitutive Nomenclature of Alcohols
  • Name as "alkanols." Replace -e ending of
    alkanename by -ol.
  • Number chain in direction that gives lowest
    numberto the carbon that bears the OH group.

CH3CH2OH
Ethanol
2-Methyl-2-pentanol
2-Hexanol
26
Substitutive Nomenclature of Alcohols
  • Hydroxyl groups outrank alkyl groups when it
    comes to numberingthe chain.
  • Number the chain in thedirection that gives the
    lowest number to thecarbon that bears theOH
    group

27
Substitutive Nomenclature of Alcohols
6-Methyl-3-heptanol
5-Methyl-2-heptanol
28
4.4Classes of Alcoholsand Alkyl Halides
29
Classification
  • Alcohols and alkyl halides are classified
    as primary secondary tertiaryaccording to
    their "degree of substitution."
  • Degree of substitution is determined by
    countingthe number of carbon atoms directly
    attached tothe carbon that bears the halogen or
    hydroxyl group.

30
Classification
H
CH3CH2CH2CH2CH2F
OH
primary alkyl halide
secondary alcohol
secondary alkyl halide
tertiary alcohol
31
4.5Bonding in Alcoholsand Alkyl Halides
32
Dipole Moments
  • alcohols and alkyl halides are polar

?

H
?
?
?
?
H
H
? 1.9 D
? 1.7 D
33
Dipole Moments
  • alcohols and alkyl halides are polar


? 1.9 D
? 1.7 D
34
Dipole-Dipole Attractive Forces
?? ?
?? ?
?? ?
?? ?
? ??
35
Dipole-Dipole Attractive Forces
?? ?
?? ?
?? ?
?? ?
? ??
36
4.6Physical Properties of Alcohols and Alkyl
HalidesIntermolecular Forces
  • Boiling point
  • Solubility in water
  • Density

37
Effect of Structure on Boiling Point
CH3CH2CH3
CH3CH2OH
CH3CH2F
Molecularweight Boilingpoint,
C Dipolemoment, D
  • 44 48 46
  • -42 -32 78
  • 0 1.9 1.7

38
Effect of Structure on Boiling Point
CH3CH2CH3
Molecularweight Boilingpoint,
C Dipolemoment, D
Intermolecular forcesare weak. Only
intermolecular forces are induced dipole-induced
dipole attractions.
  • 44
  • -42
  • 0

39
Effect of Structure on Boiling Point
CH3CH2F
A polar moleculetherefore dipole-dipoleand
dipole-induceddipole forces contributeto
intermolecular attractions.
Molecularweight Boilingpoint,
C Dipolemoment, D
  • 48
  • -32
  • 1.9

40
Effect of Structure on Boiling Point
CH3CH2OH
Highest boiling pointstrongest
intermolecularattractive forces. Hydrogen
bonding isstronger than other dipole-dipole
attractions.
Molecularweight Boilingpoint,
C Dipolemoment, D
  • 46
  • 78
  • 1.7

41
Figure 4.4 Hydrogen bonding in ethanol
?
?
?
?
42
Figure 4.4 Hydrogen bonding in ethanol
43
Boiling point increases with increasingnumber of
halogens
Compound Boiling Point
  • CH3Cl -24C
  • CH2Cl2 40C
  • CHCl3 61C
  • CCl4 77C

Even though CCl4 is the only compound in this
list without a dipole moment, it has the highest
boiling point. Induced dipole-induced dipole
forces are greatest in CCl4 because it has the
greatest number of Cl atoms. Cl is more
polarizable than H.
44
But trend is not followed when halogenis fluorine
Compound Boiling Point
  • CH3CH2F -32C
  • CH3CHF2 -25C
  • CH3CF3 -47C
  • CF3CF3 -78C

45
But trend is not followed when halogenis fluorine
Compound Boiling Point
  • CH3CH2F -32C
  • CH3CHF2 -25C
  • CH3CF3 -47C
  • CF3CF3 -78C

Fluorine is not very polarizable and induced
dipole-induced dipole forces decrease with
increasing fluorine substitution.
46
Solubility in water
  • Alkyl halides are insoluble in water.
  • Methanol, ethanol, isopropyl alcohol
    arecompletely miscible with water.
  • The solubility of an alcohol in waterdecreases
    with increasing number of carbons (compound
    becomesmore hydrocarbon-like).

47
Figure 4.5 Hydrogen Bonding Between Ethanol and
Water
48
Density
  • Alkyl fluorides and alkyl chlorides areless
    dense than water.
  • Alkyl bromides and alkyl iodides are more dense
    than water.
  • All liquid alcohols have densities of about 0.8
    g/mL.

49
4.7Preparation of Alkyl Halides fromAlcohols
and Hydrogen Halides
  • ROH HX ? RX H2O

50
Reaction of Alcohols with Hydrogen Halides
ROH HX ? RX HOH
  • Hydrogen halide reactivity HF HCl HBr HI

51
Reaction of Alcohols with Hydrogen Halides
ROH HX ? RX HOH
  • Alcohol reactivityCH3OH RCH2OH R2CHOH
    R3COHMethanol Primary Secondary Tertiary

52
Preparation of Alkyl Halides
25C
(CH3)3CCl H2O
  • (CH3)3COH HCl

78-88
53
Preparation of Alkyl Halides
A mixture of sodium bromide and sulfuric acid may
be used in place of HBr.
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