Carboxylic acids Flashcards
1
Q
Carboxylic acid
A
COOH (image)
2
Q
Carboxylic acids are
A
Dimeric
3
Q
Dimeric
A
Consisting of two similar molecules that have been linked together
4
Q
Low Pka
A
strong acid
5
Q
high pka
A
weak acid
6
Q
strength of alkanes as an acid
A
very weak acid
7
Q
are carboxylic acids strong or weak acids
A
most are weak acids
8
Q
pKa table
A
draw table out
9
Q
electronegativity
A
a measure of the ability of an atom in a chemical compound to attract electrons
10
Q
inductive effects
A
stabilize charge through sigma bonds
11
Q
electron-withdrawing substituents increase
A
acidity of nearby atom
12
Q
electron withdrawing groups effect increases with ____ and decreases with ______
A
electronegativity, distance
13
Q
Rank chlorine, iodine, fluorine and bromine in order of increasing electronegativity
A
F > Cl > Br > I
14
Q
A carboxylic acid with F as a substituent is ___ acidic than one without
A
more
15
Q
two methods of preparing carboxylic acids
A
1) oxidation in aqueous conditions 2) addition of Grignard or alkyl lithium reagents to CO2
16
Q
carboxylic acids ____ undergo nucleophilic substitution with negatively charged nucleophiles
A
do NOT
17
Q
LiAlH4 will reduce _____ to _____
A
carboxylic acids, primary alcohols
18
Q
reduction using LiAlH4
A
1) deprotonation
2) addition of hydride
3) elimination
4) addition of hydride
5) protonation
(Image)
19
Q
Acid chloride
A
Image
20
Q
Anhydride
A
Image
21
Q
Ester
A
Image
22
Q
Amide
A
Image
23
Q
Nucleophilic substitution
A
A type of substitution reaction in which a nucleophile is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond.
24
Q
Addition elimination mechanism
A
1) add to carbonyl
2) elimination of leaving group
25
Nucleophilic acyl substitution
1) Nucleophilic addition
2) elimination of the leaving group and reformation of the carbonyl (Image)
26
Golden rule of acid base reactions
stronger acids and stronger base should react to give a weaker acid and a weaker base
27
Four derivatives ranked by reactivity
Acid Chloride > anhydride > ester > amide
28
Two nucleophilic acyl substitutions that don't work
Anhydride into acid chloride ester into anhydride
29
Conversion of carboxylic acids to acid halides
1) chloride is a bad nucleophile
2) leaving group must be worse than chloride
3) leaving group disintegrates making the reaction irreversible
4) requires SOCl2, HCl, and SO2 gas
30
Mechanism of carboxylic acids to acid halides
1) attack on thionyl chloride
2) additon of Cl- to carbonyl carbon
3) elimination of SO2Cl
4) deprotonation
31
Reaction of carboxylic acid with alcohols to make esters
Requires an acid catalyst (H2SO4) and an alcohol
32
Esterfication
The reaction of an alcohol with a carboxylic acid to produce an ester and water (Image)
33
Using an excess of alcohol drives the esterification equilibrium towards the
Ester product
34
Equal concentrations of alcohol and acid
65% ester
35
10 fold excess of alcohol to acid
97% ester
36
100 fold excess of alcohol to acid
99% ester
37
Mechanism of esterfication
Image
38
Backwards reaction of esterfication
Hydrolysis
39
Mechanism of hydrolysis
Image
40
Ester hydrolysis is best done under ____ conditions
basic
41
Amides are the product of a net condensation reaction between a
carboxylic acid and an amine
42
Consequence of partial double bond character
Restricted rotation
43
For amides, interconversion of conformers is slow due to
significant double bond character of C-N bond
44
Amides react with acid at the
Oxygen
45
Amine N-H bonds are less acidic than
Amide N-H bonds
46
Brute force method of amide synthesis from acids
Wrong method. Carboxylic acids and amines form salts through acid base reactions
47
Pyrolysis
The decomposition of organic matter by heat
48
Right way to prepare amides from acids
Combination of amines and carboxylic acids int he presence of a dehydrating reagent such as DCC
49
DCC
Image
50
Mechanism of preparing amines from carboxylic acids
1) deprotonation of acid
2) attack on DCC
3) addition
4) proton transfer
5)elimination
51
Basic hydrolysis of amides requires
Strong base and heat
52
Mechanism of basic amide hydrolysis
1) Addition
2) Elimination
3) Deprotonation
53
Lactams
cyclic amides
54
Best condones for hydrolysis of amides
Acidic conditions, need more mild conditions than the conditions required for basic conditions
55
Mechanism of acid hydrolysis of amide
Image
56
What explains high reactivity
Resonance forms
57
Non aromatic compounds are ____ reactive than aromatic compounds
More
58
Strecker reaction
Image
59
Hydrolysis of nitriles to carboxylic acids requires
Aqueous acid
60
Mechanism of nitrile hydrolysis
Image
61
Under gentle reaction conditions, the hydrolysis of nitriles stops at
the amide
62
In acyl halide reactivity _____ loses every time
Chloride
63
Features of lithium tri-t-butoxy aluminium hydride
- less reactive than LiAlH4
- cannot reduce carboxylic acids
- Use of one equivalent reduces acid chlorides to aldehydes
-Catalytic hydrogenation also works
64
Reduction of acyl halides
Image
65
Mechanism of reception of acid halides
1) addition of hydride
2) elimination of halides
3) deprotonation
4) acid workup
66
Hydrolysis of esters under basic conditions requires
NaOH and acid workup
67
Mechanism of ester hydrolysis
Image
68
Cyclic esters can undergo
basic hydrolysis
69
Saponification
the reaction between a fat and a strong base to produce glycerol and the salt of a fatty acid (soap)
70
Transesterification
The process that transforms one ester to another when an alcohol acts as a nucleophile and displaces the alkoxy group on an ester.
(Image)
71
Mechanism of transesterfication under acidic conditions
1) protonation
2) addition
3) deprotonation
4) protonation
5) elimination
6) deprotonation
72
Mechanism of transesterfication
1) nucleophilic addition
2) elimination
73
Facts about acidic transesterfication
All steps in equilibrium
equilibrium favours whichever alcohol is present in greater concentration
74
Lactone
Image
75
DiBal
Image
Ester to aldehyde
76
Mechanism of reduction of esters to aldehydes using DiBal
1) Coordination of oxygen to Lewis acid aluminium
2) addition of hydride
3) addition of mild acid workup with warming
77
Reduction of nitriles with DIBal
Image
78
Why is an Al-O bond so strong
Electronegativity and charge differences
79
Mechanism reduction of amides to amines using LiAlH4
1) addition of hydride
2) elimination
3) addition of hydride
image
80
Mechanism of reduction of nitriles to primary amines with LiALH4
1) addition to nitrile
2) addition to C=N
3) mild acid workup
81
factors associated with acidity
inductive effects
resonance delocalization
electronegativity of neighbouring groups
82
esters are ___ than aldehydes or ketones
less
83
enolates are most nucleophilic at
carbon
84
enolate
intermediate
stabilized by resonance
enol+ base----- enolate
85
where does the negative charge on enolate sit
the oxygen
86
enolate formation requires the C-H bond align parallel to
carbonyl bond
87
enolizable
must have a C-H on the alpha carbon
88
keto-enol tautomerism via enolates
Break C-H
Form O-H
Break C-O
Form C-C
Form O-H
89
Deuterium labeling
Image
90
Racemate
a mixture containig equal amounts of two enantiomers
91
Chiral centres on enolates alpha carbons undergo
racemization
92
Cause of racemates
addition is able to occur at the top and bottom of the attack site
93
Chiral
a molecule that is not superimposable on its mirror image
94
epimerzation
the reversible interconversion of epimers
95
Epimer
Diasteromers that differ at only one chiral centre
Imgae
96
When do epimers occur
When the alpha carbon is chiral and there is more than one chiral centre and it is treated with a base
97
Facts about halogenation of enolates
Non selective under basic conditions
hard to control under basic conditions
multiple halogenation can occur
98
acid catalyzed halogenation of ketones
can halogenate only one or two a-H's
use acetic acid as solvent and catalyst Image
99
Halogenation of enolates
Image
