Abstract: In the present investigation we have collected 48 sets of vertical ionization potentials of two direction extending system from UV photo-electron spectroscopy and found they fit the following linear equation I_p(n,k) = a + bX(n,k) where I_p(n,k) is the kth ionization potential of the nth member of the homologous series, a and b are constant, X(n,k) is called the homologous energy factor and is equal to X(n,k)= (2k- 1)/k sin (kπ/2N +1) 60.4 % of the correlation are of the "excellent" grades with correlation factor r≥0.99,and 35.4% of the"good "grades with r≥0.95 and others with r≥0.90.Also we have discussed the hyperconjugative effect of∏₄⁴.