Identification of C5H8 isomers through reactions of singlet methylene, CH2(ã1A1), with unsaturated hydrocarbons using capillary gas chromatography-mass spectrometry

Abstract

Kováts retention indices of C₅H₈ isomers were determined by capillary gas chromatography with mass spectral detection on a capillary column combination (OV-1 and SE-54 stationary phases) and on a PoraPLOT Q molecular sieve column, at room temperature and in the temperature range 160–180 °C, respectively. Commercially unavailable isomers were identified as products of the reactions for singlet methylene with buta-1,3-diene, but-1-yne, but-2-yne and methylenecyclopropane with kinetics in the high-pressure regime. In the identification, helpful aids were (i) comparison of retention times with authentic samples (standards); (ii) using the spectral library and computer search facilities of a gas chromatographic-mass spectrometric instrument; (iii) applying chemical evidence, analogies and literature data (e.g., product ratios); and (iv) utilising boiling-point correlations (elution order). On these slightly polar columns, the main factor affecting the retention is the boiling-point, although the correlation between retention indices and boiling-points is weak for prediction purposes.