Mass Spectra of Some Deuteroethanes

Area of Science:

• Physical Chemistry
• Isotope Effects
• Mass Spectrometry

Background:

• Deuteroethanes are isotopically substituted analogs of ethane, crucial for studying reaction mechanisms and isotope effects.
• Understanding the fragmentation patterns of deuteroethanes in mass spectrometry provides insights into chemical bond strengths and molecular structures.

Purpose of the Study:

• To investigate the mass spectral characteristics of seven out of nine possible deuteroethanes.
• To analyze the influence of deuterium substitution on molecular ion abundance and fragmentation patterns.
• To compare experimental data with theoretical predictions for C-C bond cleavage and methyl radical dissociation.

Main Methods:

• Measurement of mass spectra for seven deuteroethane isotopologues.
• Normalization of mass spectra to compare ion abundances across different molecules.
• Analysis of fragmentation patterns, focusing on C1 peaks.
• Computation of weighting factors for hydrogen (H) and deuterium (D) loss, and for H+ and D+ fragment ions.

Main Results:

• Significant variations (nearly twofold) in molecular ion abundances were observed among the studied deuteroethanes.
• Distinct fragmentation patterns were noted for the two C2H4D2 isomers.
• Experimental C1 peaks were compared with patterns predicted by simple C-C bond breaking and methyl radical dissociation models.
• Weighting factors for H, D, HD, and 2D loss from C2HD5, as well as H+ and D+ ions for all deuteroethanes, were computed.

Conclusions:

• Deuterium substitution markedly influences the stability of the molecular ion and the fragmentation pathways in ethane.
• Mass spectrometry is a sensitive tool for differentiating between various deuteroethane isotopologues and elucidating their fragmentation mechanisms.
• The study provides valuable data for understanding isotope effects in chemical systems and validating theoretical models of molecular dissociation.