Download 3.20Thiols

3.20 Thiols
 Contain the functional group -SH
 Named by adding thiol to the name of the
longest carbon chain
 Number the -SH group in longer chains
CH3-SH
methanethiol
CH3-CH2SH
ethanethiol
SH
CH3-CH-CH3
2-propanethiol
Thiols (cont.)
 Many thiols have disagreeable odors
 Used to detect gas leak
 Found in onions, oysters, garlic and oysters
Onions CH3CH2CH2-SH 1-propanethiol
Garlic CH2= CHCH2-SH 2-propene-1-thiol
Skunk spray
CH3
trans-2-butene-1-thiol
CH = CH
CH2SH
and 3-methyl-1-butanethiol
Oxidation of Thiols
1. Thiols also undergo oxidation by a loss of
hydrogen atoms from the –SH groups.
2. The oxidized product is called a disulfide.
R1—S—H + H—S—R2
[O]
R1—S—S—R2 + H2O
Much of the protein in the hair is cross-linked by
disulfide, which occur between the thiol groups of
the amino acid cysteine.
1. When a person is given a “perm”, a reducing
substance is used to break the disulfide bonds.
2. While the hair is still wrapped around the curlers,
an oxidizing substance is applied that cause new
disulfide bonds to form between different parts of
the person hair strands, which gives the hair a
new shape.
COOH
COOH
NH2—CH—CH2SH + HSCH2—CH—NH
Cysteine
[O]
COOH
COOH
NH2—CH—CH2—S—S—CH2—CH—NH2