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Maclean MJ, Walker S, Wang T, Eichinger PC, Sherman PJ, Bowie JH: Diagnostic fragmentations of adducts formed between carbanions and carbon disulfide in the gas phase. Org Biomol Chem. 2010 Jan 21;8(2):371-7. Epub 2009 Oct 23.
A joint experimental and theoretical study.. Selected carbanions react with carbon disulfide in a modified LCQ ion trap mass spectrometer to form adducts, which when collisionally activated, decompose by processes which in some cases identify the structures of the original carbanions. For example (i) C (6) H (5)(-) + CS (2)--> C (6) H (5) CS (2)(-)--> C (6) H (5) S (-) + CS, occurs through a 3-membered ring ipso transition state, and (ii) the reaction between C (6) H (5) CH (2)(-) and CS (2) gives an adduct which loses H (2) S, whereas the adduct (s) formed between o-CH (3) C (6) H (5)(-) and CS (2) loses H (2) S and CS. Finally, it is shown that decarboxylation of C (6) H (5) CH (2) CH (2) CO (2)(-) produces the beta-phenylethyl anion (PhCH (2) CH (2)(-)), and that this thermalized anion reacts with CS (2) to form C (6) H (5) CH (2) CH (2) CS (2)(-) which when energized fragments specifically by the process C (6) H (5) CH (2) CH (2) CS (2)(-)--> C (6) H (5) CH (2)(-) CHC (S) SH --> [(C (6) H (5) CH (2) CH [double bond, length as m-dash] C [double bond, length as m-dash] S) (-) SH] --> C (6) H (5) CH (2) CCS (-) + H (2) S. Experimental findings of processes (ii) and (iii) were aided by deuterium labelling studies, and all reaction profiles were studied by theoretical calculations at the UCCSD (T)/6-31+G (d,p)//B3LYP/6-31+G (d,p) level of theory unless indicated to the contrary. |
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