Dehydro-oxazole, thiazole and imidazole radicals: insights into the electronic structure, stability and reactivity aspects.

DFT (U)B3LYP/cc-pVTZ and (U)M06-2X/cc-pVTZ and multireference CASSCF/cc-pVTZ level of theories have been used to investigate the electronic structure of isomeric dehydrooxazole (1b-d, 3 isomers), dehydrothiazole (2b-d, 3 isomers) and dehydroimidazole (3a-d, 4 isomers) radicals. The ground state electronic structure of each radical isomer has been confirmed by predicting their doublet excited state structure and calculating the adiabatic energy difference. The stability order of the individual isomeric radicals has been estimated through the comparison of absolute energies.

Signatures of isomerization in photodissociation of trans- crotonaldehyde probed by multiphoton ionization mass spectrometry.

We report the observation of new isomerization effects in the UV-photodissociation of trans-crotonaldehyde upon multiphoton excitation by the third harmonic (355 nm) pulses of a Nd:YAG laser. A time-of-flight mass spectrometric analysis reveals formation of acetaldehyde, acetyl, and methoxy radical cations as signatures of isomerization processes. A small segment of the multiphoton ionization spectrum of jet-cooled crotonaldehyde is recorded by tuning the laser frequency around 355 nm.

UV photolysis of α-cyclohexanedione in the gas phase.

Ultraviolet absorption spectrum of α-cyclohexanedione (α-CHD) vapor in the wavelength range of 220-320 nm has been recorded in a 1 m long path gas cell at room temperature. With the aid of theoretical calculation, the band has been assigned to the S(2) ← S(0) transition of largely ππ* type. The absorption cross section at the band maximum (∼258 nm) is nearly 3 orders of magnitude larger compared to that for the S(2) ← S(0) transition of a linear α-diketo prototype, 2,3-pentanedione.

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...

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...