ALIPHATIC CHAINS IN CALIXARENE DERIVATIVES E. F. Paulus, Hoechst AG, D-65926 Frankfurt/Main; V. Böhmer, R. Arnecke, R. A. Jakobi, W. Wasikiewicz Universität D-55099 Mainz, Germany.

The following 3 calixarenes with aliphatic chains were investigated by single crystal x-ray structure analysis:

In compound (I) two aliphatic chains (CH₂)₄O are connecting the two calices of a couple calixarene of the head-to-tail type, in compound (II) four aliphatic chains CH₃(CH₂)_l0 are substituents at the 4 bridging methylene groups and in compound (III) four of the six hydroxyl groups have the substituents CH₃(CH₂)₉. It can immediately be seen from the figures, that the aliphatic chains are mostly unfolded, backfolding is relatively seldom and occurs usually at the end of the chain. The following table gives the corresponding torsion angles, beginning at the hydroxyl ((I), (III)) or alkyl ((II)) end of the chain. Molecule (II) is on a special position and has therefore only two independent chains.

That these conformations of but low energy, but at the same time of low entropy, can occur, seems to be favoured by the high flexibility of the calixarenes. This can be seen by the fact, that the calixarene molecules are on special positions of not as high order of symmetry as is theoretically thinkable.