Naslov
Intrinsic electronic effects in organophosphate leaving groups

Autori
Matić, Mirela ; Denegri, Bernard

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
26. Hrvatski skup kemičara i kemijskih inženjera s međunarodnim sudjelovanjem - Knjiga sažetaka / Galić, Nives ; Rogošić, Marko - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI), 2019, 130-130

ISBN
978-953-6894-67-3

Skup
26. hrvatski skup kemičara i kemijskih inženjera (26HSKIKI) ; 4. simpozij Vladimir Prelog

Mjesto i datum
Šibenik, Hrvatska, 09.04.2019. - 12.04.2019

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
organophosphate, solvolysis, intrinsic electronic effects, NBO analysis

Sažetak
Kinetic measurements of solvolysis reactions of benzhydryl substrates (Bh—LG) have revealed that dimethyl phosphate is a better leaving group than related methyl carbonate and acetate for 4 and 5.5 orders of magnitude, respectively. Furthermore, the aromatic variant of the phosphate leaving group, diphenyl phosphate, is more reactive than dimethyl phosphate for 2 orders of magnitude. Replacing methyl with phenyl moiety in the carbonate leaving group leads to the increase in reactivity for 1.4 orders of magnitude, while the same structural change has a negligible impact on the reactivity of a carboxylate leaving group. Quantum mechanical calculations performed in the gas phase demonstrate similar relations in stabilities of the mentioned anions toward the benzhydryl carbocation. These results imply that strong orbital stabilizing effects develop on the heterolytic reaction coordinate of organic phosphates and finally stabilize both a solvolytic transition state and a free phosphate anion. NBO analysis indicates that orbital stabilizing effects in organic phosphates are not localized solely within the phosphinyl moiety (—PO2—), but rather transfer the anionic charge toward the methoxy moieties in dimethyl phosphate and the phenoxy moieties in diphenyl phosphates. Analogously, negative hyperconjugation delocalizes the anionic charge toward alkoxy and aryloxy moieties in alkyl and aryl carbonate anions, respectively. On the other hand, alkyl and aryl moieties in carboxylates stabilize the anionic charge only by polar effects.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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