A mathematic model for proton affinity of organic molecules: Effect of size, chain length and nature of surrounding groups on the proton affinity of a site

•A mathematic model was proposed to predict proton affinity (PA) of molecules.•The model contains structural and chemical properties of the molecules.•The PAs predicted by the model are in excellent agreement with experiments.

A mathematic model is proposed for proton affinity (PA) of organic molecules which accounts for the effects of size and nature of the functional groups and their distances from the proton acceptor atom. The general form of the proposed equation is PA(n)=A+∑iBini+∑j≥i(Bj−Bi)nj−i−C¯n2, where Bn   and C¯n2 show effect of nature and size of functional groups, respectively. A, B and C are constants and n is the number of groups directly connected to the proton acceptor site. The Bj–Bi term accounts for the effect of branched alkyl chains.

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