Post on 25-Jan-2016
description
transcript
Chemistry 2100
Lecture 5
C
O
R'R
CO R'R
C
O
HR R CHO
NomenclatureIUPAC names for aldehydes– To name an aldehyde, change the suffix -ee of
the parent alkane to -alal.– Because the carbonyl group of an aldehyde can
only be at the end of a parent chain and numbering must start with it as carbon-1, there is no need to use a number to locate the aldehyde group.
– For unsaturated aldehydesunsaturated aldehydes, indicate the presence of a carbon-carbon double bond by changing the ending of the parent alkane from -aneane to -enalenal. Numbering the carbon chain begins with the aldehyde carbonyl carbon. Show the location of the carbon-carbon double bond by the number of its first carbon.
Nomenclature• The IUPAC system retains common
names for some aldehydes, including these three.
CHO
H
OCHO
OCH3
OHtrans-3-Phenyl-2-propenal
(Cinnamaldehyde; inoil of cinnamon)
Benzaldehyde(in almonds)
Vanillin(from vanilla
beans)
NomenclatureIUPAC names for ketones.– The parent alkane is the longest chain
that contains the carbonyl group.– Indicate the presence of the carbonyl
group by changing the -aneane of the parent alkane -oneone.
– Number the parent chain from the direction that gives the carbonyl carbon the smaller number.
– The IUPAC retains the common name acetone for 2-propanone.O
Acetone 2-Methylcyclohexanone5-Methyl-3-hexanone
OO
12
34
56
12
NomenclatureTo name an aldehyde or ketone that also contains an -OH (hydroxyl) or -NH2 (amino) group:– Number the parent chain to give the
carbonyl carbon the lower number.– Indicate an -OH substituent by hydroxy-hydroxy-,
and an -NH2 substituent by amino-amino-.
– Hydroxyl and amino substituents are numbered and alphabetized along with other substituents.
O
H
OOH
NH2
3-Hydroxy-4-methylpentanal 3-Amino-4-ethyl-2-hexanone
1345 12346
Nomenclature
Common namesThe common name for an aldehyde is derived from the common name of the corresponding carboxylic acid. – Drop the word "acidacid" and change the suffix -icic or -
oicoic to -aldehyde.aldehyde.
• Name each alkyl or aryl group bonded to the carbonyl carbon as a separate word, followed by the word "ketoneketone”. Alkyl or aryl groups are generally listed in order of increasing molecular weight.O
CH3CH
O
CH3COH
Acetaldehyde Acetic acid Ethyl isopropyl ketoneMethyl ethyl ketone
OO
Physical Properties
Physical Properties
pentanebutanal2-butanone1-butanolpropanoic acid
Name Structural FormulaMolecular
Weight (amu)
72727274
74
367680
117
141
bp(°C)
CH3CH2 CH2CH2CH3CH3CH2 CH2CHO
CH3CH2 CH2CH2OHCH3CH2 COOH
CH3CH2 COCH3
diethyl ether 74 34CH3CH2 OCH2CH3
Preparations
(1°)
R HC
O
aldehyde
[O] [O]
H
O
C ORcarboxylic acid
(2°)
[O]
H
O
C ORcarboxylic acid
R
HO
C H
H R
HO
C
H
R'
ketone
R C
O
R'[O]
(1°)
R HC
O
aldehyde
[O] [O]
H
O
C ORcarboxylic acid
(2°)
[O]
H
O
C ORcarboxylic acid
R
HO
C H
H R
HO
C
H
R'
ketone
R C
O
R'[O]
(1°)
R HC
O
aldehyde
[O] [O]
H
O
C ORcarboxylic acid
(2°)
[O]
H
O
C ORcarboxylic acid
R
HO
C H
H R
HO
C
H
R'
ketone
R C
O
R'[O]
(1°)
R HC
O
aldehyde
[O] [O]
H
O
C ORcarboxylic acid
(2°)
[O]
H
O
C ORcarboxylic acid
R
HO
C H
H R
HO
C
H
R'
ketone
R C
O
R'[O]
(1°)
R HC
O
aldehyde
[O] [O]
H
O
C ORcarboxylic acid
(2°)
[O]
H
O
C ORcarboxylic acid
R
HO
C H
H R
HO
C
H
R'
ketone
R C
O
R'[O]
Reactions
C
O H
Z
O
C
H Z+
Z = C, H
C
O H
Z
O
C
H Z+
Z = C, H
C
O H
Z
O
C
H Z+
Z = C, H
C
O H
Z
O
C
H Z+
Z = C, H
C
O H
Z
O
C
H Z+
Z = C, H
C
O H
Z
O
C
H Z+
Z = C, H
C
O H
Z
O
C
H Z+
Z = C, H
Z = C, H
C
O H
Z
O
C
H Z+
C
O H
Z
O
C
Z = X, O, N
H Z+
C
O H
Z
O
C
Z = X, O, N
OH
H Z+
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
OC
H
CH3
+ OCH2 CH3H
dry HCl
orTsOH / C6H 6
H+
C
H
CH3 O
O CH2 CH3
H
hemiacetal (full) acetal
H2 O+C
H
CH3 O
O CH2 CH3
CH2 CH3
H+
(xs)HOCH 2CH 3
H+
H+
H2 O
CH 3OH
ketal
+C
CH3
CH3 O
O CH3
CH3
hemiketal
C
CH3
CH3 O
O CH3
H
CH 3OHC
CH3
CH3
O
H+
H+
H2 O
CH 3OH
ketal
+C
CH3
CH3 O
O CH3
CH3
hemiketal
C
CH3
CH3 O
O CH3
H
CH 3OHC
CH3
CH3
O
H+
H+
H2 O
CH 3OH
ketal
+C
CH3
CH3 O
O CH3
CH3
hemiketal
C
CH3
CH3 O
O CH3
H
CH 3OHC
CH3
CH3
O(xs)
H+
H+
H2 O
CH 3OH
ketal
+C
CH3
CH3 O
O CH3
CH3
hemiketal
C
CH3
CH3 O
O CH3
H
CH 3OHC
CH3
CH3
O(xs)
H+
H+
H2 O
CH 3OH
ketal
+C
CH3
CH3 O
O CH3
CH3
hemiketal
C
CH3
CH3 O
O CH3
H
CH 3OHC
CH3
CH3
O(xs)
OC
C
H
C
C
O
H
OH
O
C C
C C
H
Cyclization
OC
C
H
C
C
O
H
OH
O
C C
C C
H
OC
C
H
C
C
O
H
OH
O
C C
C C
H
OC
C
H
C
C
O
H
OH
O
C C
C C
H
OC
C
H
C
C
O
H
OH
O
C C
C C
H
OC
C
H
C
C
O
H
OH
O
C C
C C
H
OH
O
C C
C C
H
C C
C
HO
C
C O
H
C O
C
CC
C
OH
H
OH
O
C C
C C
H
C C
C
HO
C
C O
H
C O
C
CC
C
OH
H
OH
O
C C
C C
H
C C
C
HO
C
C O
H
C O
C
CC
C
OH
H
O
HO
OH
OH
H
O
CH2OH H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O
1
23
5
6
4
1
2
3
5
6
4
1
23
5
6
4
glucose
O
HO
OH
OH
H
O
CH2OH
H
O
HO
OH
OH
H
O
CH2OH H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O
1
23
5
6
4
1
2
3
5
6
4
1
23
5
6
4
glucose
O
HO
OH
OH
H
O
CH2OH
H
O
HO
OH
OH
H
O
CH2OH H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O
1
23
5
6
4
1
2
3
5
6
4
1
23
5
6
4
glucose
O
HO
OH
OH
H
O
CH2OH
H
O
HO
OH
OH
H
O
CH2OH H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O
1
23
5
6
4
1
2
3
5
6
4
1
23
5
6
4
glucose
O
HO
OH
OH
H
O
CH2OH
H
O
HO
OH
OH
H
O
CH2OH H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O
1
23
5
6
4
1
2
3
5
6
4
1
23
5
6
4
glucose
O
HO
OH
OH
H
O
CH2OH
H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O1
2
3
5
6
4
1
23
5
6
4 glucose
O
HO
OH
OH
H
O
CH2OH
H
O
HO
OH
OH
H
O
CH2OH H
C
CH2OH
OHH
HO H
H OH
H O
H
H
O
1
23
5
6
4
1
2
3
5
6
4
1
23
5
6
4 glucose
O
HO
OH
OH
H
O
CH2OH
H
23
5
6
4
1
O
H
H
H
H
HO
HO
OHOH
CH2OH
H
-glucose
Reduction• The carbonyl group of an aldehyde or
ketone is reduced to an -CHOH group by hydrogen in the presence of a transition-metal catalyst.– Reduction of an aldehyde gives a primary
alcohol.– Reduction a ketone gives a secondary
alcohol. H2
transition metal catalyst+H
O
PentanalOH
1-Pentanol
H2
transition metal catalyst
+O
Cyclopentanone
OH
Cyclopentanol
Reduction
• Reduction by NaBH4 does not affect a carbon-carbon double bond or an aromatic ring.
HCO
1. NaBH4
2. H2O
CH2OH
Cinnamaldehyde Cinnamyl alcohol
O NaBH4O-
HH3O+ O-H
H
H - C O H C O - H3O+
H C O-H: +
Hydrideion
Benedict
Tollens
O
O
RC
H
O
RC + Ag
0Ag(NH3)2 +
OH-
H2O Cu2O++ Cu
+2 (citrate)
H
O
RC
O
O
RC
H2O
OH-
Keto-Enol Tautomerism
'
H
CCCC C C
O
'
'
H
CCCC C C
O
'
'
H
CCCC C C
O
'
'
H
CCCC C C
O
'
'
H
CCCC C C
O
'
'
H
CCCC C C
O
'
'
H
CCCC C C
O
'
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
"enolizable"
H
C
O
C
enol
keto
C
O
C
H
tautomers
CH3 HC
O
CH2
?
CH3 HC
O
CH2
H ?
CH3 HC
O
CH
H CH3 HC
O
CH2
H H
C
O
C CH3CH3
H
CH3
CH
O
C CH2CH3
CH3
H
CH
O
C CH3CH3
CH3
HH
H H
C
O
C CH3CH3
H
CH3
CH
O
C CH2CH3
CH3
H
CH
O
C CH3CH3
CH3
HH
H H
H H
C
O
C CH3CH3
H
CH3
CH
O
C CH2CH3
CH3
H
CH
O
C CH3CH3
CH3
HH
H H
H H
C
O
C CH3CH3
H
CH3
CH
O
C CH2CH3
CH3
H
CH
O
C CH3CH3
CH3
HH
H H
H H
CH3
O
OH
H
O
CH3OH
H
OH
CH3
OH
CH3
O
OH
H
O
CH3OH
H
enediol
OH
CH3
OH
CH3
O
OH
H
O
CH3OH
H
enediol
OH
CH3
OH
H
H
CH3
O
OH
H
O
CH3OH
H
enediol
OH
CH3
OH
H
H
CH3
O
OH
H
O
CH3OH
H
enediol
OH
CH3
OH
H
H
O
O
O
CH OH
CH2 OH
HOH
O
O
HO OH
CH OH
CH2 OH
O
O
O
CH OH
CH2 OH
HOH
O
O
O
CH OH
CH2 OH
HOH
O
O
HO OH
CH OH
CH2 OH
O
O
O
CH OH
CH2 OH
HOH
O
O
O
CH OH
CH2 OH
HOH
O
O
HO OH
CH OH
CH2 OH
O
O
O
CH OH
CH2 OH
HOH
glyceraldehyde
3-phosphate
OPO3-2
H
CH2
OH
HOC
Cketonize
enolize
enolize
ketonize
OPO3-2
C OH
CH
CH2
OH
enediol
OPO3
-2CH2
O
OHCH2
C
dihydroxyacetonephosphate
glyceraldehyde
3-phosphate
OPO3-2
H
CH2
OH
HOC
Cketonize
enolize
enolize
ketonize
OPO3-2
C OH
CH
CH2
OH
enediol
OPO3
-2CH2
O
OHCH2
C
dihydroxyacetonephosphate
glyceraldehyde
3-phosphate
OPO3-2
H
CH2
OH
HOC
Cketonize
enolize
enolize
ketonize
OPO3-2
C OH
CH
CH2
OH
enediol
OPO3
-2CH2
O
OHCH2
C
dihydroxyacetonephosphate
glyceraldehyde
3-phosphate
OPO3-2
H
CH2
OH
HOC
Cketonize
enolize
enolize
ketonize
OPO3-2
C OH
CH
CH2
OH
enediol
OPO3
-2CH2
O
OHCH2
C
dihydroxyacetonephosphate
glyceraldehyde
3-phosphate
OPO3-2
H
CH2
OH
HOC
Cketonize
enolize
enolize
ketonize
OPO3-2
C OH
CH
CH2
OH
enediol
OPO3
-2CH2
O
OHCH2
C
dihydroxyacetonephosphate
glyceraldehyde
3-phosphate
OPO3-2
H
CH2
OH
HOC
Cketonize
enolize
enolize
ketonize
OPO3-2
C OH
CH
CH2
OH
enediol
OPO3
-2CH2
O
OHCH2
C
dihydroxyacetonephosphate
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
fructose-6-phosphate
HHO
H OH
H OH
CH2O PO3-2
OH
O
CH2
enolize
ketonize
enediol
CH
OH
HHO
H OH
H OH
CH2O PO3-2
OH
glucose-6-phosphate
ketonize
enolize
HHO
H OH
H OH
CH2O PO3-2
OHH
CO H
Carboxylic Acids
Carboxylic Acids
• In this chapter, we study carboxylic acids, another class of organic compounds containing the carbonyl group.
• The functional group of a carboxylic acid is a carboxyl groupcarboxyl group, which can be represented in any one of three ways.
CO2HCOOHC-OHO
Nomenclature
IUPAC names– For an acyclic carboxylic acid, take the
longest carbon chain that contains the carboxyl group as the parent alkane.
– Drop the final -ee from the name of the parent alkane and replace it by -oic acidoic acid.
– Number the chain beginning with the carbon of the carboxyl group.
– Because the carboxyl carbon is understood to be carbon 1, there is no need to give it a number.
Nomenclature
– In these examples, the common name is given in parentheses.
– An -OH substituent is indicated by the prefix hydroxy-; an -NH2 substituent by the prefix amino-.
3-Methylbutanoic acid(Isovaleric acid)
Hexanoic acid(Caproic acid)
OH
O
OH
O1 1
63
OH
OOHH2N COOH
5-Hydroxyhexanoic acid
15
4-Aminobenzoic acid
Nomenclature– To name a dicarboxylic acid, add the
suffix -dioic aciddioic acid to the name of the parent alkane that contains both carboxyl groups; thus, -aneane becomes -anedioic anedioic acidacid.
– The numbers of the carboxyl carbons are not indicated because they can be only at the ends of the chain.O
HOOH
O
Butanedioic acid(Succinic acid)
Ethanedioic acid(Oxalic acid)
Hexanedioic acid(Adipic acid)
Propanedioic acid(Malonic acid)
HO OH
O
OOH
O
OH
O
O
HO
O
HO
1 1
1 1
2 3
4 6OH
O
HO15
O
Pentanedioic acid(Glutaric acid)
Nomenclature
CH3COOHHCOOH
CH3CH2COOHCH3(CH2)2COOHCH3(CH2)3COOHCH3(CH2)4COOHCH3(CH2)6COOHCH3(CH2)8COOHCH3(CH2)10COOHCH3(CH2)12COOHCH3(CH2)14COOHCH3(CH2)16COOHCH3(CH2)18COOH
DerivationCommon Name
IUPAC Name(acid)Structure
Greek: arachis, peanutGreek: stear, solid fatLatin: palma, palm treeGreek: myristikos, fragrantLatin: laurus, laurelLatin: caper, goatLatin: caper, goatLatin: caper, goatLatin: valere, to be strongLatin: butyrum, butterGreek: propion, first fatLatin: acetum, vinegarLatin: formica, ant
arachidicstearicpalmiticmyristiclauric
capriccapryliccaproicvalericbutyricpropionicaceticformic
eicosanoicoctadecanoichexadecanoictetradecanoicdodecanoicdecanoicoctanoichexanoicpentanoicbutanoicpropanoicethanoicmethanoic
Nomenclature
For common names, use, the Greek letters alpha (), beta (), gamma (), and so forth to locate substituents.
C-C-C-C-OHO
OHH2N
O
OHOH
O
(-Aminobutyric acid; GABA)2-Hydroxypropanoic acid4-Aminobutanoic acid
4 3 2
1
4
1
2
(-Hydroxypropionic acid;lactic acid)
Physical Properties
H3C C
O
O
H
CH3C
O
O
H- +
+ -
hydrogen bondingbetween two molecules
Physical PropertiesCarboxylic acids are more soluble in water than are alcohols, ethers, aldehydes, and ketones of comparable molecular weight.
CH3COOHCH3CH2CH2OHCH3CH2CHO
CH3(CH2)2COOHCH3(CH2)3CH2OHCH3(CH2)3CHO
acetic acid
1-propanolpropanal
60.5
60.158.1
1189748
16388.1butanoic acid1-pentanol 88.1 137
103pentanal 86.1
Structure NameMolecularWeight
Boiling Point (°C)
Solubility(g/100 mL H2O)
infinite
infinite
16infinite
2.3slight
larger Ka increased [H3O+] stronger acid
A– + H3O+
[HA][A–] [H3O+]
Ka =
HA + H2O
larger Ka increased [H3O+] stronger acid
A– + H3O+
[HA][A–] [H3O+]
Ka =
HA + H2O
increased [H3O+] stronger acid
A– + H3O+
[HA][A–] [H3O+]
larger Ka
Ka =
HA + H2O
larger Ka increased [H3O+] stronger acid
A– + H3O+
[HA][A–] [H3O+]
Ka =
HA + H2O
RCOOH + H2O RCOO– + H3O+
[RCOOH][RCOO–] [H3O+]
Ka =
RCOOH + H2O RCOO– + H3O+
[RCOOH][RCOO–] [H3O+]
Ka =
acids > phenols ~ thiols > water ~ alcohols
Ka % ionized [H3O+], M pH
~1 107 ~100 ~0.1 1.00
1.8 10–5 1.3 1.3 10–3 2.88
3.3 10–10 0.0036 3.6 10–6 5.44
2.5 10–11 0.0016 1.6 10–6 5.80
1.3 10–16 0.0001 1.0 10–7 7.00
HCl
HOAc
PhOH
EtSH
EtOH
HOH
Comparative acidities of 0.1 M aqueous solutions of representative acids HA
1.8 10–16 0.0001 1.0 10–7 7.00
Fatty AcidsTable 18.3 The Most Abundant Fatty Acids in Animal Fats, Vegetable Oils, and Biological Membranes.
Unsaturated Fatty Acids
Saturated Fatty Acids
20:4
18:3
18:2
18:1
16:1
20:0
18:0
16:0
14:0
12:0
Carbon Atoms:Double Bonds*
Melting Point(°C)
Common NameStructure
-49
-11
-5
16
1
77
70
63
58
44
arachidonic acid
linolenic acid
linoleic acid
oleic acid
palmitoleic acid
arachidic acid
stearic acid
palmitic acid
myristic acid
lauric acid
CH3(CH2)1 2COOH
CH3(CH2)1 0COOH
CH3(CH2)1 4COOH
CH3(CH2)1 6COOH
CH3(CH2)1 8COOH
CH3(CH2)7 CH=CH(CH2 )7COOH
CH3(CH2)5 CH=CH(CH2 )7COOH
CH3(CH2)4 (CH=CHCH2 )2(CH2)6 COOH
CH3CH2 (CH=CHCH2 )3(CH2)6 COOH
CH3(CH2)4 (CH=CHCH2 )4(CH2)2 COOH
* The first number is the number of carbons in the fatty acid; the second is the number of carbon-carbon double bonds in its hydrocarbon chain.
Fatty AcidsUnsaturated fatty acids generally have lower melting points than their saturated counterparts.
COOH
COOH
COOH
COOH
Stearic acid (18:0)(mp 70°C)
Oleic acid (18;1)(mp 16°C)
Linoleic acid (18:2)(mp-5°C)
Linolenic acid (18:3)(mp -11°C)
Fatty AcidsSaturated fatty acids are solids at room temperature.– The regular nature of their hydrocarbon
chains allows them to pack together in such a way as to maximize interactions (by London dispersion forces) between their chains.
COOH
COOH
COOH
COOH
COOH
Fatty Acids
In contrast, all unsaturated fatty acids are liquids at room temperature because the cis double bonds interrupt the regular packing of their hydrocarbon chains.
COOH
COOH
COOH
COOH
COOH
Soaps
Soaps
Decarboxylation
• DecarboxylationDecarboxylation: The loss of CO2 from a carboxyl group.
• Almost all carboxylic acids, when heated to a very high temperature, will undergo thermal decarboxylation.
• Most carboxylic acids, however, are resistant to moderate heat and melt and even boil without undergoing decarboxylation.
• An exception is any carboxylic acid that has a carbonyl group on the carbon to the COOH group.
O
RCOH RH CO2decarboxylation +
high temperature
Decarboxylation
• Decarboxylation of a -ketoacid.
• The mechanism of thermal decarboxylation involves (1) redistribution of electrons in a cyclic transition state followed by (2) keto-enol tautomerism.
OH
OO O
CO2Acetone3-Oxobutanoic acid
(Acetoacetic acid)
+warm
O OH
O
OH
C
O
O
OCO2
+
enol ofa ketone
(A cyclic six-membered transition state)
(1) (2)
Decarboxylation• An important example of decarboxylation of
a -ketoacid in biochemistry occurs during the oxidation of foodstuffs in the tricarboxylic acid (TCA) cycle. Oxalosuccinic acid, one of the intermediates in this cycle, has a carbonyl group (in this case a ketone) to one of its three carboxyl groups.
COOHCOOH
O
HOOC COOH
O
HOOC CO2+
Oxalosuccinic acid
only this carboxyl has a C=O beta to it.
-Ketoglutaric acid