Modified NPOH Equation Showing Terminal Effect: Boiling point of homologs monosubstituted alkanes (RX)

Abstract

Effect of terminal group on the changes in physicochemical properties (P(n)) of homologs monosubstituted alkanes (RX) is still unclear topic. In this work, take the boiling points (Tb) of 15 homologs RX as examples; the effects of terminal X on the Tb were investigated, in which the X involves F, Cl, Br, I, OH, CN, NH2, CO2H, CHO, SH, C6H5, CH=CH2, C≡CH, c-C5H9, and c-C6H11. A general equation expressing the Tb of the homologs RX was proposed, named the NPOH Equation Showing Terminal Effect, as follows: ln (Tb (n)) = a + b(n-1) + cSCNE + dItg, where Itg is the terminal effect and its attenuation coefficient is 1/n. The results show that this equation is more accurate to express the Tb change of homologs RX than the NPOH equation in our previous paper. The parameter Itg has important influence on the Tb of RX, while it has less influence on the Tb of homologs α,ω-disubstituted alkanes XRX and can be ignored. The Tb changes of 15 homologs RX and homolog alkane can be expressed using a general equation (Equation 11 in text). The effect of intramolecular charge-induced dipole μind on the boiling point of homologs RX cannot be ignored.