CHAPTER 17 – ALDEHYDES & KETONES
Carbonyl Group:
-CO
Aldehydes: compounds containing a carbonyl group
attached to H and an alkyl or aromatic group or another H.
General formula: R-C-H
O
Examples
H3C-C-H
H-C-H
O
O
C-H
O
Naming Aldehydes
Same as alkanes, with these additional rules.
1. The longest chain must include the aldehyde group.
O
2. The suffix “al” represents the -C-H group (replace
ending “e” with “al”).
Example
H
O
H – C –H
H–C–H
H
methane
(formaldehyde)
H
H
H–C – C–H
H
H
Ethane
Name this compound:
H
H
H
H–C– C–C–C –H
H
H
H
O
Note: No number is needed in the name to identify the
location of the aldehyde group because the aldehyde group
is always located at the end of the chain.
3. If groups are attached to the parent, assign the lowest
possible number to the carbon of the aldehyde group.
O
CH3-CH2-CH2-CH-C-H
CH2
CH3
Ketones: compounds containing a carbonyl group attached
to two alkyl or aromatic groups (or one alkyl & one
aromatic).
General formula: R-C-R’
O
Examples
H3C-C-CH3
O
C-CH3
O
Naming Ketones
Same as alkanes, with these additional rules.
1. The longest chain must include the ketone group.
O
2. The suffix “one” represents the -C- group (replace
ending “e” with “one”).
Example
H
H
H
H–C–C–C–H
H H H
propane
H
O
H
H–C–C–C–H
H
H
Can you have methanone?
3. When assigning numbers to the carbons in the parent
chain, assign the lowest possible number to the carbon
attached to the =O
Examples
Br
H3C-C-CH2-CH2-CH3
O
H3C-CH2-C-CH2-CH-CH3
O
Name these compounds:
Cl
H3C-C-CH2-CH2-C-CH3
CH3
O
CH3
H3C-C-CH2-CH2-C-CH2 CH3
CH3
O
H3C-CHCH-CH2-C-H
F F
O
Name the functional groups in this compound.
OH
OCH3
Vanillin
C-H
O
Oxidation of Aldehydes
R-C-H
[O]
O
Aldehyde
R-C-O-H
O
carboxylic acid
[O] = oxidizing agent (adds oxygen or loss of hydrogen)
(oxygen in air is a mild oxidizing agent)
R-C-R’
[O]
no reaction
O
Ketone
In lab we can differentiate between an aldehyde and a
ketone based on if they react with an oxidizing agent.
Silver Mirror Test
Tollens’ Reagent: oxidizing agent (contains silver nitrate &
ammonia in water)
R-C-H + 2Ag(NH3)2+
O
Aldehyde
3[OH-]
R-C-OH + 2Ag + 4NH3
O
carboxylic acid silver mirror
Benedict’s Test
Benedict’s Solution: oxidizing agent (contains Cu2+ ions, in
a basic solution; blue color)
R-C-H
+
2Cu2+
O
Aldehyde
[O]
R-C-O-
+
Cu2O
O
carboxylic acid orange/red ppt
Positive test for an aldehyde: blue color disappears &
red/orange precipitate forms.
Complete the following reactions by drawing the structural
formula of the organic product formed in the reaction:
O
CH3-CH2-CH2-CH2-C-H + Benedict's sol’n
O
CH3-CH2-CH2-C-CH3
+ Benedict's sol’n
4. Aldehyde or ketone groups take precedence over other
groups (i.e. alkene, alkyne, alcohol).
H2C=CH-CH2-C-CH3
O