4th EucheMs chemistry congress

wednesday, 29-Aug 2012
s656
chem. Listy 106, s587–s1425 (2012)
Environment and Green Chemistry
Green Chemistry – ii
o - 2 9 4
deSiGninG Greener PLAStiCizerS: infLuenCe
of GeoMetry of CentrAL GrouP And Side
ChAinS
h. C. erythroPeL 1 , r. L. LeASK 1 , M. MAriC 1 ,
d. G. CooPer 1
1 McGill University, Chemical Engineering, Montreal, Canada
Plasticizers are important additives for brittle polymers such
as poly(vinyl chloride) (PVC). Their addition lowers the glass
transition temperature (Tg) making the blends soft and flexible.
Because plasticizers are not bound to the polymer matrix, they
slowly leach out of the blend into the environment. Many studies
have shown di (2-ethylhexyl phthalate) (DEHP) and some of its
toxic stable metabolites such as its monoester (MEHP) to be
ubiquitous environmental contaminants due to their slow
breakdown by soil bacteria. This has led to efforts to design new,
“green” plasticizers.
Small diester molecules that resemble DEHP were formed
from maleic or succinic acid and esterified with alcohols ranging
from ethanol to n-octanol and 2-ethyl hexanol were prepared and
tested for their plasticizer properties such as reduction of Tg
and tensile strength in blends with PVC. To assess their
biodegradability, the compounds were exposed to the common
soil bacterium Rhodococcus rhodocrous to determine hydrolysis
rates and metabolite buildup.
Studies with 2-ethylhexyl diesters showed the importance
of the geometry of the central structure in diester plasticizers on
biodegradation. When the two esters were in a cis-position to one
another (maleate), the hydrolysis step of the diester was hindered,
while for the saturated succinate, which was free to rotate about
the intervening bond, was quickly hydrolysed. Also, no buildup
of monoester could be observed for the succinate. Both
compounds showed comparable plasticizer properties to DEHP.
On this basis, further studies were undertaken with linear
succinate compounds in order to avoid the production of a known
toxic metabolite (2-ethyl hexanoic acid). Plasticizer properties
were similar to the branched compounds and improved with the
overall length of the diester. Hydrolysis rates increased when no
branching was present, and were inversely proportional to chain
length. The data suggest these small diester molecules are green
plasticizers.
Keywords: Green Chemistry; Environmental Chemistry;
Polymers;
Green Chemistry – ii
4 th EucheMs chemistry congress
o - 2 9 5
BALL MiLLinG: An eMerGinG tooL for
orGAniC SyntheSiS
A. StoLLe 1 , r. SChMidt 1 , r. thorwirth 1 ,
t. SzuPPA 1 , f. BernhArdt 1 , B. ondruSChKA 1
1 Friedrich-Schiller University Jena, Institute for Technical
Chemistry and Environmental Chemistry, Jena, Germany
Over the last two decades a major trend in the field of
Organic Chemistry could be observed: environmentally friendly
processes using safer reagents, generating fewer side products, as
well as a decreased utilization of solvents are en vogue. Taking
advantage of this general trend, the performance of reactions
under ball milling conditions in the absence of solvents is an
increasing field of research, resulting in various publications
covering this topic from synthetic point of view, not only
dedicated to organic but also to inorganic chemistry as well as to
materials and polymer science.
Due to the high energy density during ball milling, reaction
times can often be kept short comparable to typical experimental
procedures with radiation based energy entry (thermal or dielectric
heating). System inherent high mixing efficiency allowed for
efficient mixing of lipophilic and hydrophilic compounds without
the need for employment of phase transfer reagents or similar
additives used in solvent-based processes. Furthermore,
continuous particle refinement accounts for the formation of small
crystallites with high defect concentration, thus high chemical
reactivity. Improving the reactivity of solid materials due to
comminution in combination with reduction of mass transport
limitations leads to high reactivity of substrates in the solid state
allowing several reactions, sometimes with unique selectivity.
Using model reactions from different fields of research like
cross-coupling, selective oxidation, or cycloaddition the
advantages and disadvantages of this technique compared to other
methods of energy entry will be demonstrated with regard to
feasibility, energy efficiency, and scale-up potential.
Overall results showed that the performance of reactions in
ball mills is often beneficial over classical experimental
procedures. Reduced reaction times, reduction of solvent
utilization, and the suppression of side reactions result in
increased yields of the target products and an improved overall
energy efficiency and mass intensity.
Keywords: solvent-free synthesis; solid-state chemistry; metal
catalyzed reactions; green chemistry; process intensification;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc