1303567-81-8Relevant articles and documents
Structure and unimolecular chemistry of protonated sulfur betaines, (CH3)2S+(CH2)nCO 2H (n = 1 and 2)
Yoo, Ellie Jung-Hwa,Feketeova, Linda,Khairallah, George N.,White, Jonathan M.,O'Hair, Richard A. J.
, p. 2751 - 2759 (2011)
The fixed charge zwitterionic sulfur betaines dimethylsulfonioacetate (DMSA) (CH3)2S+CH2CO 2- and dimethylsulfoniopropionate (DMSP) (CH 3)2S+(CH2)2CO 2- have been synthesized and the structures of their protonated salts (CH3)2S+CH2CO 2H...Cl- [DMSA.HCl] and (CH3) 2S+(CH2)2CO2H... Pcr- [DMSP.HPcr] (where Pcr = picrate) have been characterized using X-ray crystallography. The unimolecular chemistry of the [M+H]+ of these betaines was studied using two techniques; collision-induced dissociation (CID) and electron-induced dissociation (EID) in a hybrid linear ion trap Fourier transform ion cyclotron resonance mass spectrometer. Results from the CID study show a richer series of fragmentation reactions for the shorter chain betaine and contrasting main fragmentation pathways. Thus while (CH 3)2S+(CH2)2CO 2H fragments via a neighbouring group reaction to generate (CH 3)2S+H and the neutral lactone as the most abundant fragmentation channel, (CH3)2S+CH 2CO2H fragments via a 1,2 elimination reaction to generate CH3S+CH2 as the most abundant fragment ion. To gain insights into these fragmentation reactions, DFT calculations were carried out at the B3LYP/6-311++G(2d,p) level of theory. For (CH3) 2S+CH2CO2H, the lowest energy pathway yields CH3S+CH2via a six-membered transition state. The two fragment ions observed in CID of (CH3) 2S+(CH2)2CO2H are shown to share the same transition state and ion-molecule complex forming either (CH3)2S+H or (CH2) 2CO2H+. Finally, EID shows a rich and relatively similar fragmentation channels for both protonated betaines, with radical cleavages being observed, including loss of CH3.
