Download aldehyde ketone

Chapter 19: Aldehydes and Ketones
O
R
O
H
aldehyde
R
R
ketone
These are carbonyl compounds that have no extra heteroatoms (an atom besides C or H)
attached that might stabilize anions and act as leaving groups
Due to the polarity of the C=O bond, a permanent dipole moment exists in aldehydes and
ketones (dipole-dipole forces). Thus, the MP/BP of aldehydes and ketones is mid-range –
higher than that of alkanes or alkenes (London forces) but lower than that of alcohols
(hydrogen bonds).
Nomenclature – IUPAC
Aldehydes: Suffix – “-al”
1. Find the longest chain that contains the aldehyde carbonyl carbon.
2. Number the chain, starting from the aldehyde carbonyl carbon (ALWAYS #1).
3. Identify the prefixes attached and their position numbers.
4. Write the full name – Prefixes – Parent – “al”.
Just like we did for alcohols, the parent name is the same as that of an alkane, just remove
the “-e” at the end and add the new suffix “-al”.
Ex:
CH3CH2CH2CH3
Butane
CH3CH2CH2CHO
Butanal
-“CHO” = aldehyde group in condensed form
Name the following:
H
O
Ketones:
1. Find the longest chain that contains the ketone carbonyl carbon.
2. Number starting from the end closest to the ketone carbonyl carbon.
3. ID the prefixes attached and their position numbers
4. Write the full name – Prefixes – # of carbonyl position - Parent – “-one”
The parent name is the same as that of an alkane, just remove the final “-e” at the end
and add “-one”.
Unlike the aldehyde, a number MUST be included for the position of the carbonyl carbon
in the chain. The number is inserted just before the parent or in front of the suffix
itself.
Ex.
CH3CH2CH2CH2CH3
Pentane
CH3C(O)CH2CH2CH3
2-Pentanone or Pentan-2-one
“C(O)” = carbonyl group in condensed form and representative of a ketone, when nothing
else is attached.
Name the following:
a.
6,6-dimethyl-3-heptanone
b.
O
O
2-methylcyclohexanone
c.
O
O
1,3-cyclohexanedione
You now know how to name a multitude of types of compounds. There is a priority order
for what functional group “controls” the numbering in a chain:
Highest
Lowest
Carboxylic Acids (Ch 20)
Esters (and other acid derivatives) (Ch 21)
Aldehydes
Ketones
Alcohols
Alkenes
Alkynes
Alkanes
Consider this molecule: What functional groups are present and which one controls the
numbering?
O
Number and name:
6,6-dimethyl-4-hepten-3-one
O
What about this example? Which direction are you going to number from?
O
A bit more information is required: A group that is named as a suffix (alkenes, alkynes)
is always given priority over a group that is only named as a prefix!
O
6-methylhept-2-en-4-one
or 6-methyl-2-hepten-4-one
In the presence of an aldehyde, a ketone is named as a prefix, “oxo”.
Ex.
H
O
5-oxoheptanal
O
In the presence of an aldehyde OR ketone, the alcohol is a lower priority and is named as
a prefix, “hydroxy”.
Name:
O
3-hydroxycyclohexanone
OH
Number and name:
O
OH
6-hydroxycyclohex-2-enone
Number and Name:
O
H
4-oxohex-2-enal
O
Name:
OH
5-hydroxy-1-phenylheptan-2-one
O
OH
8-hydroxynon-2-en-5-one
O
Other nomenclature methods:
Simple ketones (similar to simple ethers):
Name the two R groups (in alphabetical order, of course) and end in “ketone”
Ex.
O
methyl methyl ketone
dimethyl ketone
methyl ketone
acetone
Ex.
O
ethyl phenyl ketone
Ex.
O
Common names:
benzyl propyl ketone
O
H
H
formaldehyde
O
H
CH3
acetaldehyde
O
H
benzaldehyde