Attempt to set up a semiquantitative theory of mutual effects of atoms in organic compounds Communication 2. Electronic charges of bonds and physical properties of molecules

Summary

• 1. Simple semiempirical equations are proposed for the relation between force constants and characteristic frequencies of bonds on the one hand and total (σ- + π-) electronic charges of bonds on the other. These equations are checked by calculation of the total electronic charges of ethylene and acetylene. The electronegativity of acetylenic carbon is determined.

• 2. It is shown that it is possible to calculate π-electronic charges of bonds by two methods which give closely agreeing results-from bond lengths and from electronegativities.

• 3. An additive scheme is proposed for the calculation of heats of formation of unsaturated hydrocarbons from their elements; the scheme is analogous to that already proposed for saturated hydrocarbons. The separate π-electronic energies of C-C and C-H bonds are calculated. Electronegativities are calculated for carbon atoms in the α- and β -positions with respect to the acetylenic bond of normal 1-alkynes.

• 4. It is shown that dipole moments of polyatomic molec,,les are generally determined by the nonintegral character of the electronic charges of individual bonds. It is possible to estimate electronegativities of atoms from from dipole moments.