Near Infrared Spectra of Compounds with Two Peptide Bonds and the Configuration of a Polypeptide Chain. III

Abstract

Infrared Spectra of Two Peptide Bonds, the Polypeptide Chain 186-3 more remote branching would not be expected to alter the curve appreciably from that of 2-methyl-2•dodecenoic acid. The absence of a 10.1 µ band in the spectrum of 2,5-dimethyl-2-heptadecenoic acid rules out at least one isomeric form of this structure. The available spectra do not provide any basis for a choice from among the other most likely structures.Note added in proof.-Recently a sample of synthetic 2,4-dimethyl-2-dodecenoic acid has become available from Professor Cason,6 and its infrared spectrum has been examined. In the region beyond 10 µ, absorption bands are found at the following wave lengths (values for the corresponding bands of C27-phthienoic acid-see Figs. 3 and 4are given in parentheses for comparison): 10.05 (10.06), 12.3 (12.50), 13.2 (13.26), 14.9 (14.92) µ. Considered together with previous evidence, these data indicate that the second branching methyl group of Cz7-phthienoic acid is in the y-position.

Conformational studies of N‐acetyl‐N′‐methylamide derivatives of α‐aminobutyric acid, norvaline, and valine. I. Preferred conformations in solution as studied by 1H‐nmr spectroscopy

“…Following By~trov,'~ we adopt the correction for the peptide fragment, and let JNH-cmH = l.09Job (2) where a factor of 1.09 has been introduced to account for the electronegativity difference between the C" substituent and hydrogen. In the literature, several sets of coefficients (A,B,C) have been proposed for Eq.…”

The crystal and molecular structure of N-acetyl-DL-phenylalanine-N-methylamide

“…Following the structural study by infrared spectroscopy carried out by Mizushima et al (1953Mizushima et al ( , 1954, Tsuboi, Shimanouchi & Mizushima (1959) and Koyama, Shimanouchi, Sato & Tatsuno (1971), an X-ray study of the crystal structures has been undertaken. Following the structural study by infrared spectroscopy carried out by Mizushima et al (1953Mizushima et al ( , 1954, Tsuboi, Shimanouchi & Mizushima (1959) and Koyama, Shimanouchi, Sato & Tatsuno (1971), an X-ray study of the crystal structures has been undertaken.…”

Изучение Водородной Связи Этилового Эфира N-Ацетил Глицина Методами Ик И Ямр Спектроскопии

“…Инфракрасные спектры растворов АГЭ в СС1 4 в области 1600-1800 и 3200-3500 с[мг х были сняты на спектрометре UR-20. Из рисунка видно, что полоса около 3330 см~1 , соответствующая валентному колебанию водорода NH, связанного водородным мостиком, при разбавлении растворов смещается в сторону больших волновых чисел, ее интенсивность уменьшается и она исчезает при концентрациях ниже 0,005 М. Такие изменения в инфракрасном спектре согласуются с данными работы [ 4 ] и показывают, что АГЭ, в отличие от эфиров глицина [ 11 ], образует только межмолекулярную Н-связь в растворе ССЦ.…”

“…Установлено, что этиловый эфир А-ацетилглицина (АГЭ) в СС1 4 образует в основном только межмолекулярную Н-связь между водородом NH и амидным кислородом. Энтальпия образования Н-связи АГЭ в СС1 4 , рассчитанная на основе ЯМР измерений, равна4,4 ккал/моль. ЛИТЕРАТУРА…”