Noun
Any
of
a
class
of
compounds
of
general formula
R
<
sub
>
1
sub
>
R
<
sub
>
2
sub
>
C
(
OH
)
OR
' (
where
R
'
is
not
H
and
R
<
sub
>
1
sub
>
or
R
<
sub
>
2
sub
>
is
often
hydrogen
).