Chemistry Reference
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Fig. 9 Versatility of the Pd-catalyzed telomerisation reaction to access short-chain
ethers of polyols, sugar alcohols and carbohydrates.
62,65-75
of bases that allow higher reaction rates but also an increased
amount of diethers. Biphasic conditions are preferentially applied for
higher selectivity towards monoethers. In this case, the 2-O-octadienyl
monoether is the main product, whereas performing the reaction in an
organic medium allows access
to the 5-O-octadienyl monoether
preferentially.
The Pd-catalyzed telomerisation of 1,3-dienes (1,3-butadiene, isoprene)
with addition of a nucleophile (telogen) is a 100%-atom economical and
versatile reaction
65
that generates few waste and can be applied to a variety
of bio-based substrates, including polyols, carbohydrates and sugar alco-
hols (Fig. 9).
66-75
It is thus an attractive access to bio-based hydrotropes.
3 Physico-chemical properties of sugar-based
hydrotropes
3.1 Volatility
Some applications of hydrotropes require exhibiting volatility, so that the
compound can slowly evaporate during the process. This property dis-
tinguishes solvo-surfactants from the other classes of hydrotropes. This
is important for instance when used as coalescing agents and/or co-
solvent for water-borne paints, in order to ensure a good formation of the
paint film during the evaporation process. The short-chain ethers of
isosorbide have proven to be ecient for this application, due to their
good compatibility with the latex particles and their proper evaporation
profile.
35
For other applications, the hydrotrope-based formula should
leave few or no residue at all after use, as for instance in hard-surface
(ex. window) cleaning. In that case also, volatility plays a major role and
should be a criterion of prior importance for the initial choice of
hydrotrope.
Glycosides, classical aromatic and ionic hydrotropes (Fig. 1) are non-
volatile, whereas some derivatives of polyols and sugar alcohols show
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