Intramolecular Hydrogen Bonds. XIII. The Preferable Conformation of α-Hydroxy-carboxylic and o-Hydroxybenzoic Acids

Abstract

The infrared hydroxyl and carbonyl stretching absorption spectra of salicylic, mandelic, and α-hydroxyisobutyric acids have been measured in dilute carbon tetrachloride solutions. The spectral data indicate that the first two acids exist exclusively in an internally-bonded conformation, one where the phenolic and the alcoholic hydroxyl groups form a hydrogen bond with the carbonyl oxygen atom of the cis-carboxyl structure, while the last acid takes, apart from such a conformation, another internally-bonded conformation, one where the hydroxyl group of the trans-carboxyl structure interacts with the alcoholic oxygen atom.

Chirality influence on the aggregation of methyl mandelate

“…The matrix isolation results are in good agreement with higher temperature solution studies. [21][22][23] The latter had revealed an internally CQO hydrogen bonded OH stretching fundamental near 3536-3551 cm À1 , together with a much weaker feature near 3603-3613 cm À1 , which was tentatively attributed to a weaker OH hydrogen bond, either to the phenyl ring or to the ester OCH 3 group. The CQO stretching fundamental was located near 1737-1739 cm À1 , and its weak overtone assigned at 3455 cm À1 , about 0.5% below the harmonic prediction.…”

“…The CQO stretching fundamental was located near 1737-1739 cm À1 , and its weak overtone assigned at 3455 cm À1 , about 0.5% below the harmonic prediction. 22 It is not detected in the matrix isolation spectra.…”

“…Methyl mandelate has been investigated before in its monomeric form by vibrational spectroscopy in CCl 4 solutions [21][22][23] and with IR/UV spectroscopy. 24 Spectra and conformational preferences as a function of aggregation state are still missing, in contrast to the extensive studies of methyl lactate, both experimental and theoretical.…”

Adaptive Aggregation and Chirality Recognition of Neuroactive Substances and their Building Blocks: A Vibrational Spectroscopic and Microscopic Study

“…Monomers and small clusters of methyl mandelate were extensively studied by FTIR-jet spectroscopy and double-resonance IR/UV spectroscopy [38,137,138]. IR and vibrational circular dichroism studies were performed on methyl mandelate in solution [139][140][141]. KBr pellet and ATR-IR spectra are reported for the solid state [38].…”

“…The enantiomeric purity in solutions can be measured by simultaneous dual circular dichroism and UV spectroscopy [159]. Solutions of mandelic acid were also investigated by IR spectroscopy [140,[160][161][162][163]. FTIR-ATR spectra of solid mandelic acid were measured as well [20,[163][164][165].…”