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Topochemistry Part XXXV. The Formation of Mixed Dimers from Solid Solutions of Trans ‐Cinnamic Acids and Trans ‐Cinnamides
Author(s) -
Hung J. D.,
Lahav M.,
Luwisch M.,
Schmidt G.M.J.
Publication year - 1972
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.197200057
Subject(s) - chemistry , miscibility , crystal structure , stereochemistry , monomer , cinnamic acid , solid state , crystallography , solid solution , amino acid , crystal (programming language) , polymer , organic chemistry , biochemistry , computer science , programming language
Irradiation ( λ >300 nm) of eight two‐component solid solutions of β ‐arylacrylamides, prepared by melting and crystallising equimolar quantities of the amides tr ‐ArCH:CHCONE where Ar=C 6 H 5 , p ‐MeOC 6 H 4 , p ‐ClC 6 H 4 , p ‐MeC 6 H 4 , and 2‐thienyl, which appeared in the α crystal form, gave three photoproducts for each system studied: two α ‐truxillic homodimers, derived from the respective monomers, and an α ‐truxillic heterodimer. No other isomers were found. Similarly, two‐component solid solutions were prepared by melting and crystallising ring‐substituted cinnamic acids ( tr ‐ArCH:CHCO 2 H, where Ar=C 6 H 5 ( α ‐form), p—ClC 6 H 4 ( β ), p ‐MeC 6 H 4 ( α ), p ‐MeOC 6 H 4 ( γ ), o ‐ClC 6 H 4 ( β ) and o ‐CH 3 C 6 H 4 ( γ )) and irradiated. A solid solution of two α ‐type acids (each photodimerising in the solid to α ‐truxillic acid) behaved like the amides, affording two α ‐truxillic homodimers and an α ‐truxillic heterodimer. A solid solution of an α ‐type acid with a β ‐type acid (photodimerising to β ‐truxinic acids) gave six photoproducts: three α ‐truxillic acid dimers and three β ‐truxinic acid dimers (i.e., four homodimers and two heterodimers). Irradiation of a solution of a γ ‐type acid (non‐photodimerising in the solid state) with an α ‐type acid afforded α ‐truxillic dimers (two homodimers and one heterodimer). The above results are consistent with mutual miscibility of the two components which gives rise to mixed crystal formation and subsequent photo‐behaviour within each crystal which is characteristic of the particular lattice type. However, irradiation of the mixed crystals from p ‐methoxycinnamic acid ( γ ‐type) and p ‐chlorocinnamic acid ( β ‐type), which afford two α ‐truxillic dimers (methoxy‐homodimer and methoxy, chloro‐heterodimer) and two β ‐truxinic dimers (chloro‐homodimer and methoxy, chloro‐heterodimer) indicates that new phases, unobserved for the pure compounds, can also be generated. The new dimers were all characterised by the NMR and mass spectra of their dimethyl ester derivatives and, when possible, by conversion to known compounds.