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Structure reactivity relationship in the accelerated formation of 2,3-diarylquinoxalines in the microdroplets of a nebuliser
Hayat, Nadia Fenwick, Nathan W. Saidykhan, Amie Telford, Richard Martin, William H.C. Gallagher, R.T. Bowen, Richard D.
Hayat, Nadia
Fenwick, Nathan W.
Saidykhan, Amie
Telford, Richard
Martin, William H.C.
Gallagher, R.T.
Bowen, Richard D.
Publication Date
2019-12-01
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2019-08-29
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Abstract
Competition experiments in which 1,2-phenylenediamine, C6H4(NH2)2, condenses with equimolar quantities of benzil, (C6H5CO)2, and a 3,3'- or 4,4'-disubstituted benzil (XC6H4CO)2 (X = F, Cl, Br, CH3 or CH3O) to form a mixture of 2,3-diphenylquinoxaline and the corresponding 2,3-diarylquinoxaline (Ar = XC6H4) in the microdroplets produced in a nebuliser allow a Hammett relationship with a ρ value of 1.85 to be developed for this accelerated condensation in the nebuliser. This structure reactivity relationship reveals that an appreciable amount of negative charge builds up on the carbon of the carbonyl group of the benzil during the rate-limiting step of the reaction, thus confirming that this process involves nucleophilic addition of the 1,2-phenylenediamine to the benzil. In general, the presence of an electron donating substituent, particularly in the 4 and 4' positions, in the benzil retards the reaction, whereas an electron attracting substituent, especially in the 3 and 3' position, accelerates it.
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Hayat N, Fenwick NW, Saidykhan A, Telford R et al (2019) Structure reactivity relationship in the accelerated formation of 2,3-diarylquinoxalines in the microdroplets of a nebuliser. European Journal of Mass Spectrometry. 25(6): 457-462.
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Letter