The electrochemical polymerizations of a series of ortho-disubstituted benzenes were investigated by experimental and theoretical approaches. The results indicated that o-dihydroxybenzene (oHDB)

o-dimethoxybenzene (oDMOB) and 1-hydroxy-2-methoxybenzene (HMOB) in pure boron trifluoride diethyl etherate (BFEE) can be succefully electropolymerized. The 1H

13C-NMR spectra of these monomers and their corresponding polymers proved that the polymerization occurred mainly at C4 and C5 positions. However the others such as o-xylene

1

2benzenedithiol

1

2-dibromobenzene

1

2-dichlorobenzene

1

2-dicyanobenzene and 1

2-dinitrobenzene can not be electropolymerized under similar conditions. These intrinsic characteristics have been revealed by the experimental investigation on these o-disubstituted benzenes together with the theoretical calculations. The cyclic voltammetry and linear sweep voltammetry were used to determine oxidation potential onset of the monomers. Optimizing the ground-state geometries of the monomer and the radical cation of HOMO

LUMO and electron spin density were calculated by using the density functional theory (DFT) at the B3LYP/631G(d

p) level. From the experimental point of view

the oxidation potential onset of the monomer is not the control factor for the electropolymerization. According to theoretical studies

the monomers substituted by electrondonating groups have more negative electronics than the monomers substituted by electron-withdrawing groups. These monomerso-DHB

oDMOB and HMOB with negative electronic charges of (C4

C5) ca. -0.093～-0.103 can be electropolymerized in BFEE. The others with the electronic changes of (C4

C5) ca. -0.078～-0.085 cannot be electropolymerized in the same media. Therefore

we can extrapolate that the negative electronic of reaction site maybe has a critical value (probobly≈|0.09|)

which is one of the condition for electropolymerization of the monomer. From the frontier molecule orbitals theory

the reactions between the active molecules mainly happens on the highest frontier electron density involving the two frontier orbitals having the smallest energy gap and obey orbital symmetry rules. Therefore

the orbital symmetry of HOMO and LUMO of the polymerization site should be matching. oHDB

oDMOB

and HMOB via α-HOMO and β-LUMO interaction having the smallest energy gap are satisfied with symmetry rules

they can be electrochemically polymerized. Whereas the others such as o-xylene

1

2-dibromobenzene

1

2-dichlorobenzene

1

2-dicyanobenzene and 1

2-dinitrobenzene via β-HOMO and α-LUMO interaction having the smallest energy were antisymmetrical

which cannot be electropolymerized. Therefore

the HOMO-LUMO orbital symmetry matching is another condition for the electrochemical polymerization of o-disubstituted benzenes.