CH⋯O H-bond mediated tautomerization of 2-methyl-1,3-cyclohexanedione: A combined IR spectroscopic and theoretical study.

Molecular association and its impact on the keto-enol tautomerization of 2-methyl-1,3-cyclohexanedione (MCHD) have been investigated in low temperature argon matrix and thin solid film. The system exists exclusively in diketo tautomeric form in argon matrix. The CH⋯O H-bonded homodimers of the diketo tautomer are produced by annealing the matrix at 28 K.

Stereo-preference of camphor for H-bonding with phenol, methanol and chloroform: A combined matrix isolation IR spectroscopic and quantum chemical investigation.

Camphor is known to be held in the substrate pocket of cytochrome P450cam enzyme via H-bond with a tyrosine residue of the enzyme in a unique orientation. This structural exclusivity results in regio- and stereo-specific hydroxylation of camphor by the enzyme. We have carried out a combined IR spectroscopic and quantum chemical investigation to shed light on the factors influencing the conformational exclusivity of 1R-(+)-camphor in the substrate pocket of Cytochrome P450cam, and to determine whether the selectivity is an inherent property of the substrate itself, or is imposed by the enzyme.

Antagonistic Interplay Between an Intermolecular CH···O and an Intramolecular OH···O Hydrogen Bond in a 1:1 Complex Between 1,2-Cyclohexanedione and Chloroform: A Combined Matrix Isolation Infrared and Quantum Chemistry Study.

Matrix isolation infrared spectra of a weak C-H···O hydrogen-bonded complex between the keto-enol form of 1,2-cyclohexanedione (HCHD) and chloroform have been measured. The spectra reveal that the intramolecular O-H···O H-bond of HCHD is weakened as a result of complex formation, manifesting in prominent blue shift (∼23 cm) of the ν band and red shifts (∼7 cm) of ν bands of the acceptor (HCHD). The ν band of donor CHCl undergoes a large red shift of ∼33 cm.

Doubly hydrogen bonded dimer of δ-valerolactam: infrared spectrum and intermode coupling.

We report here the vibrational analysis of the infrared spectrum of doubly hydrogen bonded dimer of δ-valerolactam measured in CCl4 solution at room temperature (22 °C). The compound shows an equilibrium of population distributed over the monomer and doubly hydrogen bonded dimer, which is manifested by the isosbestic point in the normalized spectra for solutions of different concentrations. Dimerization induced changes in transition frequencies and intensities have been measured and compared with the computed results.

CH···O interaction lowers hydrogen transfer barrier to keto-enol tautomerization of β-cyclohexanedione: combined infrared spectroscopic and electronic structure calculation study.

Molecular association and keto-enol tautomerization of β-cyclohexanedione (β-CHD) have been investigated in argon matrix and also in a thin solid film prepared by depositing pure β-CHD vapor on a cold (8 K) KBr window. Infrared spectra reveal that, in low-pressure vapor and argon matrix, the molecules are exclusively in diketo tautomeric form. The CH···O hydrogen bonded dimers of the diketo tautomer are produced by annealing the matrix at 28 K.

Blue- and red-shifting CH...O hydrogen bonded complexes between haloforms and ethers: correlation of donor nu(C-H) spectral shifts with C-O-C angular strain of the acceptors.

In 1:1 CH...

Cooperative strengthening of an intramolecular O-H...O hydrogen bond by a weak C-H...O counterpart: matrix-isolation infrared spectroscopy and quantum chemical studies on 3-methyl-1,2-cyclohexanedione.

Matrix-isolation infrared spectra of 1,2-cyclohexanedione (CD) and 3-methyl-1,2-cyclohexanedione (3-MeCD) were measured in a nitrogen matrix at 8 K. The spectral features reveal that, in the matrix environment, both molecules exist exclusively in the monohydroxy tautomeric form, which is stabilized by an intramolecular O-H..

Blue shifting C-H...O hydrogen bonded complexes between chloroform and small cyclic ketones: ring-size effects on stability and spectral shifts.

Blue-shifting C-H...