Download Functional Groups - SISIBChemistry2012

Functional Groups
- The reactive portion of a molecule that undergoes predictable
reactions. We have already looked at alkenes, alkynes and
haloalkanes.
- Functional groups are attached to the carbon chain, which is
represented by R, which means the rest of the carbons.
- Solubility in water depends on a molecules’ polarity.
- Volatility depends on the intermolecular forces present.
Alcohols (Alkanols) R –OH
- A hydrocarbon that has a hydrogen replaced by an -OH group.
- They are named by replacing the ‘e’ in the alkane name with ‘ol’.
The longest chain of carbons must contain the carbon with the –
OH attached.
1-butanol
2-butanol
2-methyl-2-propanol
(1º)
(2º)
(3º)
- The highlighted carbons are used to name the type of alcohol.
This depends on the number of carbons atoms adjacent to the
carbon containing the –OH.
O
Aldehydes (Alkanals) R- C – H (carbonyl group)
- The condensed way of writing an aldehyde is RCHO, with the O
written last, not to be confused with the alcohols RCOH.
- To name this functional group, count the carbons in the longest
chain and replace the ‘e’ ending with ‘al’. No number is necessary,
as the aldehyde will always occur on the end of a carbon chain.
methanal (formaldehyde)
ethanal
O
Ketones (Alkanones) R – C – R’ (RCOR’)
- Similar to an aldehyde, but there is a carbon group on either
side of the carbonyl group. It is named with a ‘one’ ending.
Carboxylic Acids (Alkanoic Acid) R- COOH (carboxylic group)
- Named with an ‘oic acid’ ending.
Esters R-COO-R’
-Similar to a carboxylic acid, except the hydrogen is replaced
with another carbon group.
- Esters are named in two parts, the carbon chain that is
attached to the carbonyl group (C=O) is named with an ‘oate’
ending and the carbon chained attached where the hydrogen
usually is attached in a carboxylic acid is named with an ‘yl’ ending.
Ethers (R-O-R’)
- Lone oxygen among two carbon chains.
- Give the name of each alkyl group in alphabetical order followed
by the word ether.
Amine (R – NH2)
- Are formed by replacing one of the hydrogen atoms in ammonia
with a hydrocarbon group.
- Amines are weak bases as the nitrogen can donate its lone pair
of electrons (Lewis base).
primary amine
secondary
tertiary
- the alkyl group is named normally followed by amine
CH3NH2
CH3NHCH2CH3
O
Amide (R- C – NH2)
- Compounds that are derived from the reaction of ammonia (or
an amine) and a carboxylic acid.
- Naming Amides: the alkyl group is named without the yl ending
and then followed by – anamide.
NH2COCH3
methylethanamide
- In terms of basicity, alkyl amines are stronger bases than
ammonia. This is due to the alkyl group stabilizing, by acting as
electron donating groups, which stabilize the cation (+ charge).
Examine the Kb values.
- However in amides, the lone pair of electrons on the nitrogen is
involved in delocalized π-bonding with the electrons in the –C=O
double bond. This means that the pair of electrons on the
nitrogen is not available to form a bond with a hydrogen ion, thus
amides are virtually non-basic. (See ethanamide diagram)
Nitriles R-CN or R-CN
- They are indirectly related to amides (by the loss of H2O from
a primary amide), and react chemically similar to carboxylic acids
and their derivatives. It should be noted that H-CN is not truly a
nitrile and is named hydrogen cyanide.
Ethanitrile
2-methylpropanenitrile