Environmental Engineering Reference
In-Depth Information
O
O
O
O
O
O
X
X
H
OR
X
=
H
,
OH
R
=
H
,
alkyl
O
X
O
n
OR
R
=
H
,
alkyl
O
O
O
O
RO
OR
O
ROH, H
+
,
Δ
Aldol
H
Cl
Cl
OR
R
=
alkyl
O
O
OR
O
RO
R
=
alkyl
O
O
O
H
O
R
n
R
=
alkyl
Figure 4.15
5-(Chloromethyl)furfural as a platform molecule.
and/or aldehyde condensation products. Under more forcing conditions, the furan
ring opens with the loss of formate to give levulinate products. Several useful
derivatives have been described, some examples of which are shown in Figure 4.15.
From the top and proceeding clockwise, complete hydrogenation of CMF gives
2,5-dimethyltetrahydrofuran, a promising fuel oxygenate [177-179]. Reaction
with water gives HMF, an icon of the renewable chemistry movement [176].
Likewise, reaction with alcohols at room temperature gives alkoxymethyl
furfurals, which have also been considered for use as biofuels [180-182]. Reaction
with either water or alcohols at higher temperatures gives levulinic acid or
levulinic esters, respectively, plus the corresponding formates [121]. Like HMF,
levulinic acid is considered a key biomass-derived platform chemical [26], while
levulinate esters have been proposed as diesel additives [183]. Further exposure of
levulinate esters to alcohols in the presence of acid (either added acid or
auto-catalytically via liberated HCl) gives levulinate ester acetals which have
applications as novel monomers, plasticisers and solvents [184]. Finally, the
hydrogenation of levulinate esters gives valeric esters, which have been shown to
possess outstanding fuel properties [185].
The Friedel-Crafts reaction was one of the first derivatisations performed on
the CMF molecule [186], and yields aryl derivatives that may be useful as biofuel
precursors [187]. Gentle hydrogenation of CMF gives 2,5-dimethylfuran, an
outstanding biofuel in its own right [188] but also highly valuable as the precursor
