Why is benzene a polar molecule, whose polarity is even greater than toluene

Why is benzene a polar molecule, whose polarity is even greater than toluene?

 

 

solvent polarity table에 보면, relative polarity의 값이 벤젠은 0.111, 톨루엔은 0.099인 이유?

 

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According to the table of the organic solvent polarity, the relative value for benzene is 0.111 and 0.099 for toluene.

 

However, theoretically speaking, benzene is non-polar due to its highly structural symmetry, and toluene is polar because of methyl group’s electron donating character.

 

벤젠의 쌍극자모멘트는 0 D이고, 톨루엔의 쌍극자모멘트는 0.36 D이다.

즉, 톨루엔이 더 극성인 용매이다.

 

The question above seems contradictory with the theoretical analysis. But the point is the conclusion that benzene's polarity is greater than toluene comes from experimental results of silica gel column chromatography.

 

In the process of the silica gel column chromatography, the more highly polar solvent we use will generally give rise to a faster washing out rate.

 

When benzene work as an eluent, the attraction between the product and benzene is generally greater than toluene’s because benzene is a flat molecule whose steric hindrance is less.

 

Thus we have such conclusion that seems opposite with the general theory. After all, chemistry is an experimental science, all right?

[ 출처: https://www.quora.com/Why-is-benzene-a-polar-molecule-whose-polarity-is-even-greater-than-toluene ]