A correlation analysis study reinvestigation of a 13 c scs for some substituted poly aromatic fused rings

Abstract EN

The substituent effect on the 13C substituent chemical shift ( SCS ) and the additively for series namely .

(1ـــ X – naphthalene (I ), (2 –X – naphthalene (II), (9 –X – anthracene (III), have been investigated by using MSP , DSP .

Tafts model was the best on the DSP model due to the wide scale of resonance parameters (O+ R, O- R, O R BA, OR O).

13C chemical shift of distant carbons could be predicted reason ably well on the basis of calculated change of electron densities.

The influences of electronic, steric and the conformational analysis of the fused system were discussed.

The fused aromatic system have a behavior differ than the simple aromatic system due to its regularity.

In this work 13 C (SCS) proved to be used as a monitor in many physical calculation like qualitative and quantative studies.

This may be lead to the field effect the difference in planarity like in COMe.

while OMe and OEt = 26 and CO2H (1.1), Cl (2), Br (-2.2).

C10 have a small effect on the substituent change and in this fused system the change in chemical shift for most of the carbon atoms was small.

So that it can not be evaluated or to estimate a reasonable feature about this difference.

The dielectric field (12) effect have been studied intensively in this type of poly cyclic aromatic rings and a separation between л – Polarization and DEF effects a not straight – forward , DEF effects were suggested to be the reason for the high field shift of the carbon atoms .

Like the high field of C – 2 in 1 – nitro – naphthalene, the electric field effect will polarize the C – H bond decrease the electron density at the proton and consequently interact at the carbon nucleus.

As 13 C chemical shifts are much more sensitive to changes in electron density than at 1H shifts, one expects the high field of the carbon resonance to be much stronger than the corresponding low field shift of the proton.