Download Carbonyls

Power Point to Accompany
Principles and Applications of
Inorganic, Organic, and Biological
Chemistry
Denniston, Topping, and Caret
4th ed
Chapter 14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
Carbonyl Compounds
Contain the carbonyl
group, C=O
Aldehydes:
R may be hydrogen
usually a carbon
containing group
Ketones:
R contains
carbon
O
R C R
O
R C H RCHO
Short
forms
O
R C R RCOR
2
14.1 Structure and Physical Properties
The carbonyl group
is polar. The oxygen
end is negative.
Carbonyls of less
than six carbons are
at least partly water
soluble. They can H
bond to water.
O +

C
O
C
H O
H
Hydrogen
bond
3
Boiling Points
Carbonyl compounds boil between alkanes
and alcohols of similar molecular weight.
O
CH3CH2CH2CH3
butane, bp -43o
O
CH3C CH3
propanone, bp 56o
CH3CH2CH
propanal, bp 50o
CH3CH2CH2OH
propanol, bp 97o
4
14.2 Nomenclature
Aldehydes
Common: H2C=O formaldehyde (a gas)
Used to make insulation and plastic
dinnerware.
Also using traditional names and Greek
letter substitution patterns. E. g.
O
Cl
CH3CH CH2CH2CH




-chlorovaleraldehyde
5
Naming Aldehydes: IUPAC Names
Base name: longest chain with the C=O
Replace the -e of alkane name with -al
O
CH3CH CH2CH2CH
CH3
4-methylpentanal
6
Naming Ketones
Common:
O
acetone, an important solvent
CH3 C CH3
Also by naming the two alkyl groups
attached to the carbonyl in a) alphabetical
order or b) by increasing size
Methyl ethyl ketone
or
Ethyl methyl ketone
O
CH3 C CH2 CH3
7
Naming Ketones: IUPAC
Base name: longest chain with the C=O
Replace the -e of alkane name with -one
Indicate position of C=O by number on chain
Cl
O
CH3CH CH2C CH3
4-chloro-2-pentanone
8
14.3 Carbonyl Examples
Methanal (b.p. –21 oC) is used in aqueous
solutions as formalin to preserve tissue and
embalm.
Acetone and methyl ethyl ketone (MEK) are
very versatile solvents.
Other examples:
CH3O
HO
O
CH
Vanillin
Vanilla beans
O
CH3 CH2 5 C CH3
2-octanone
Mushroom flavor
9
14.4 Reactions of Carbonyls
Aldehydes are prepared from primary
alcohols by oxidation with a mild oxidizer,
eg (CrO3/py), pyridinium dichromate
Example: Note: this oxidation removes two
hydrogens. It is also an oxidative
elimination reaction.
CrO3
CH3CH2CH2OH
in py
O
CH3CH2CH
or
H2CrO4
10
Preparation of Ketones
Prepared from 2o alcohols
by oxidation with Cr(VI) or Mn(VII)
species
OH
KMnO4 or
K2Cr2O7 or
CrO3,py
O
The oxidation removes two hydrogens and forms
a double bond. It is also an elimination reaction!
11
Reactions of Carbonyls
1. Redox
a) Aldehydes: oxidized to carboxylic acids
b) Aldehydes and ketones are reduced to
alcohols: aldehydes to primary alcohols
and ketones to secondary alcohols
2. Addition
a) of hydrogen to give alcohols
b) of alcohols to give hemiacetals, acetals,
hemiketals, and ketals
c) of aldehydes/ketones to give aldol (hydroxy carbonyl) products
12
Oxidation of Aldehydes
Aldehydes are easily oxidized to
carboxylic acids by almost any
oxidizing agent.
Visual tests for the aldehyde functional
group based on its easy oxidation are:
Tollen’s Test
Silver ion is the oxidizer, as Ag(NH3)2 +
Benedict’s Test
Cu2+ in a basic solution is the oxidizer.
Solution is a distinctive blue color.
Color fades with rxn.
13
Oxidation of Aldehydes-2
O
O
KMnO4
CH3CH
CH3C O
H2O, OH
O H CrO
2
4
CH
O
C OH
Tollen’s test uses silver ion and gives a
silver mirror on the glass reaction
container
O
O
+
Ag(NH3)2
CH3CH2C O
CH3CH2CH
As mirror
+ Ag on test tube14
Oxidation of Aldehydes-3
Fehling’s test uses copper ion. The blue
color fades giving a red ppt of Cu2O.
(Often used to test for simple reducing
sugars.) O
O O
H
C
C
H C OH
H
C
OH
HO C H 2 Cu2+ HO C H
H C OH OHH C OH
H C OH
H C OH
CH2OH
CH2OH
+ Cu2O
15
Reduction of Carbonyls
Reduction occurs with hydrogen.
The reaction is also an addition reaction.
O
CH3CH2C CH3
OH
CH3CH2CH CH3
H2 Pt,
O Pd, Ni
OH
CH3CH2CH2CH
CH3CH2CH2CH2
16
Additions to Carbonyls: Alcohols
Carbonyls add one molecule of alcohol
to give usually unstable hemiacetals
and hemiketals
O
CH3CH2CH2CH + CH3OH
OH
CH3CH2CH2CH
O CH3
Hemiacetal(ketal) carbons are
H+
part of both alcohol and ether
functions and are a new
functional group
OH
O
+
H
CH3CH2C CH3
CH3CH2C CH3 + CH3OH
O CH3
17
Additions to Carbonyls: Alcohols-2
Acid catalyzes both aldehydes and
ketones to react with two molecules of
alcohol to give acetals and ketals
O
O CH3
+
H
CH3CH2CH + 2 CH3OH
CH3CH2CH
O CH3
Acetal(ketal) carbons are part of two
ether groups and are a new
functionalOgroup
CH3CH2C CH3 + 2 CH3OH
H+
O CH3
CH3CH2C CH3
O CH3
18
Additions to Carbonyls: Alcohols-3
Glucose forms a cyclic hemiacetal when
the alcohol group on C-5 reacts with
the aldehyde group C=O.
hemiacetal
carbon
this H is involved
in hemiacetal
formation
CH2OH
OH
C
O
OH
H
OH
OH
hemiacetal link
forms here
CH2OH
O OH
OH C
H
OH
OH
19
Hydrolysis of (Hemi)acetals/ketals
Both hemiacetals and acetals (and ketone
analogs) hydrolyze (react with water). An
acid catalyst takes them back to the
carbonyl compound and the alcohol(s).
O CH3
H+
CH3CH2CH + H2O
acetal O CH3
O
CH3CH2CH
+ 2 CH3OH
O
OH
+
H
CH3CH2C CH3
CH3CH2C CH3
+ CH3OH
hemiketal O CH3
20
Keto-enol Tautomers
Tautomers are isomers which differ in the
placement of an atom of hydrogen and a
double bond. The keto form has a C=O
while the enol form has a C=C.
The keto form is usually the most stable.
H O
R1 C C R3
R2
H O
H C CH
H
R1
OH
C C
R2
R3
OH
H C C H
H
21
Additions to Carbonyls:
Aldol Condensation
Self Addition or Condensation
Uses two molecules of the same
aldehyde or ketone.
The alpha carbon of the second
molecule adds to the carbonyl carbon
of the first molecule.
Strong base such as hydroxide
catalyzes the reaction.
22
Aldol Condensation-2
Self Addition/Condensation: aldehyde
An aldol has an OH beta to the carbonyl
group
OH
O
O
O
OHCH3CH CH2CH
CH3CH + CH3CH
alpha carbon,
second
molecule
original
alpha
carbon
carbonyl carbon of first molecule becomes alcohol carbon
in aldol
23
Aldol Condensation: Aldolase
Dihydroxyacetone phosphate +
D-glyeraldehyde-3-phosphate
1
2-
1
2CH2 OPO3
CH2 OPO3
2
2
C O
C O
3
H C OH aldolase H 3C OH
Bond formed
4
H
H5C O H
4
H5C O
HC OH
26
HC OH
OPO
CH
3
2
26
D-fructose-1,6-bisphosphate
CH2 OPO3
Alpha carbon (3) adds to carbonyl carbon (4).
(Gluconeogenesis)
24
The End
Carbonyl
Compounds
25