INFRARED ABSORBING GROUPS IN $CYCLO-(HEXACLYCYL)^{*}$

Abstract

The IR spectrum of cyclo-(hexaglycyl) the material being kindly provided by Ballard Bam ford and Wesmonth, has been studied between 4000 and $615\, cm^{-1}$ using KBr pellets of mixtures shaen in a virbator with and without steel balls for various time intervals. The crystalline material is mainly prismatic with some pseudo-hexagonal $plates^{1}$. X-ray $investigations^{2}$ of the prismatic crystals reveal unit cell contents corresponding to varius multiples of mono- or hemi-hydrates of the $(CH_{2}CONH)_{6}$ molecule. Since the BBW material is derived from glycyl N-Carbonic anhydride polymers, formed by orthopeptide bonds, it seems Probable that in these crystals internet $N-C(OH)$ bonds, typical of $cyclol-groupings^{2}$, are maintained leading to $OH\ldots O$ trimers, analogous to those demonstrated by NMR investigations as characteristic of associated primary $alcohols^{4}$. On the peripheries proton transfer must occur. The prismatic dimensions reported by Cant are satisfied if a-axis inter-associations occur between 1, 1 N-diacyl and 1, 1 diamino carbinols, the Carbinols being associated through bound water to carbonyls in successive layers in the c-axis direction. Peripheral inter-associations would occur between cyclic CONH and chelated $CO-N-C(OH)-NH$ groups. Absorption frequencies characteristic of such hydrogen-bonded configurations are identified. Moderate shaking with steel balls appears to result in increased peripheral inter-moleculaar association at the expense of the internal $OH\ldots H$ trimerss, prolonged shaking resulting in small peptide fractions of the basic units. These conclusions result from comparison of frequencies and intensities in the spectra of various fractions with those of primary alcohols, inositol, diacetyls, and chelated molecules. $CH_{2}$ frequencies are correlated with those in the spectra of substituted cyclohexanes and selected steroids.