Transcript othschem.pbworks.com

Groups 11,12 and 13
Carboxylic Acids, Ethers and
Esters
Today's Starter Quote
“What lies behind us and what
lies before us are tiny matters
compared to what lies within
us”
– Ralph Waldo Emerson
Oxidation of an alcohol will lead to an aldehyde or ketone.
Further oxidation can lead to the formation of a carboxylic
acid, where both an aldehyde and alcohol functional group
are found. The overall appearance is -COOH where the
group must be terminal.
B. R. Travis, M. Sivakumar, G. O. Hollist, B. Borhan, Org. Lett., 2003, 5, 1031-1034.
Note: Ketones will not oxidize under standard
conditions. So we will consider that ketone + (O) → NR
Aldehydes will test positive by the Tollen's test, whereas a
ketone will not react in this manner.
(chem.wisc.edu)
Carboxylic acids are named by taking the typical alkane
name and changing the suffix from ‘ane’ to ‘anoic acid’.
Examples:
1)
HCOOH
methanoic acid (formic acid)
found in
ant bites
(gcsescience.com/methanoic-acid)
2)
CH3COOH
ethanoic acid
(acetic acid)
found
in vinegar
(gcsescience.com/ethanoic-acid)
3)CH3CH(OH)COOH
2-hydroxypropanoic acid
(lactic acid)
(bmrb.wisc.edu)
Many common organic compounds contain more than one
COOH group such as tartaric acid found in grapes, citric
acid in fruits, ascorbic acid (Vitamin C) and acetylsalicylic
acid found in aspirin.
Carboxylic acids are quite polar since they have both an
OH group and a carbonyl group. They are quite similar to
alcohols, however have the characteristics of acids such
as turning litmus paper red (an excellent test for this
group only) and neutralizing base.
Ethers
The structure of an ether is similar to water. Rather than a
hydrogen on each side of the oxygen atom, there are carbon
chains.
The two groups may be identical (ROR)or different( R –O-R’).
There is no possibility to form hydrogen bonds since there are
no OH groups, however the boiling point is intermediate
between the alkane and alcohol as they are somewhat polar.
Ethers are good solvents since they mix well with polar and
non-polar liquids. They are unreactive due to the trapped O,
which makes it an even better solvent.
Ethers are named by adding oxy to the smaller group and
joining it to the alkane name of the longer chain.
Examples:
CH3CH2OCH2CH2CH3
CH3OCH3
CH3OCH2CH3
ethoxypropane
methoxymethane
methoxyethane
Ethers are made by condensation reactions. This is another
word for a dehydration reaction. By adding two alcohols in
the presence of strong acid, it is possible to make an ether.
H2SO4
Example: CH3OH + CH3CH2OH --> CH3OCH2CH3 + HOH
Methanol ethanol
methoxyethane
water
Esters:
Formation of an ester occurs when a carboxylic acid is
reacted with an alcohol in the presence of a strong acid and
heat. The result is an ester with the group C(=O)O-R where R
is another alkyl group. Water is also made.
Esters are easily characterised by their distinct odour, often
used in artificial flavouring. The reaction may occur as :
Acid and heat
Butanoic acid + methanol --> methyl butanoate + water
(an apple odour)
NOTE: when naming esters, the first part of the name is
derived from the part that came from the alcohol. It also will not
have a carbonyl group. The second part of the name comes
from the carboxylic acid that retains the carbonyl group.
Examples:
ethyl benzoate
octyl ethanoate
ethyl butanoate
ethyl methanoate
C6H5COOCH2CH3
CH3COO(CH2)7CH3
CH3CH2CH2COOCH2CH3
HCOOCH2CH3