X-ray structure determinations have been carried out and analyzed for two conformational polymorphs
of α-truxillic acid (2). Polymorph I (cell parameters known since 1959) is isolated upon recrystallization of 2 from
acetic acid−petroleum ether solution, while polymorph II (fully characterized in 1993) is the product of a one-phase
solid-state reaction of tail-irradiated α-cinnamic acid. For polymorph II, two redeterminations of mixed crystals
containing solid solutions of α-cinnamic acid and 2 (68.1 and 89.5%, respectively) were performed. Analysis of the
structural parameters of the 1993 and present redeterminations of the polymorph II structures, as well as comparison
to data from the Cambridge Structural Database, confirm that claims of errors in the 1993 structure determination
of polymorph II are unfounded. X-ray quality crystals of the β-polymorph of trans-cinnamic acid (cell parameters
known since 1964) have been obtained from Et2O/petroleum ether solutions; the crystal structure is quite similar to
that of 4-chlorocinnamic acid.
Irradiation ( 60 Co g-rays) of crystalline bis(but-3-enoato)zinc, a two-dimensional coordination polymer with a bilayer packing motif, affords isotactic zinc poly(but-3-enoate).
The regeneration of LB films of
(trimethylsilyl)cellulose (TMSC) (1) to ultrathin films
of cellulose (2)
is monitored by X-ray photoelectron spectroscopy (XPS). Subsequent
chemical derivatization of these
regenerated cellulose films with trifluoroacetic anhydride (TFAA)
(3) to give the corresponding cellulose
trifluoroacetate (5) was proven and followed by XPS as a
function of exposure time in order to study
hydroxyl accessibility. The derivatization behavior of regenerated
cellulose films is compared with literature
data on bulk cellulose materials with varying degrees of crystallinity.
In contrast to the latter, the
functionalization kinetics of the regenerated cellulose films indicates
a low hydroxyl accessibility in conjuction
with a high degree of order in these films.
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