Orientation of Benzene
ORIENTATION IN BENZENE | ||
ORIENTATION IN BENZENE | ||
| All hydrogen atoms of the benzene ring are equivalent. Therefore, when a group enters into the benzene ring, only one monosubstituted product (C6H5-G) is possible as described below: | ||
| Problem starts when another group (E+) or second substituent enters into monosubstituted benzene and it can occupy any one of the remaining five positions as shown below:. | ||
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| But which one of the five positions the new group will occupy??? Let us discuss the exact possibility. | ||
EFFECT OF SUBSTITUENTS ON FURTHER SUBSTITUTION | ||
| Positions 2 and 6 are same (ortho product) Positions 3 and 5 are same (meta product) Position 4 is para position | ||
INFLUENCE OF SUBSTITUENT | ||
A substituent (G) already present on the benzene ring imparts two types of influence on benzene ring for further substitution. Directive effect Activity effect | ||
DIRECTIVE OR ORIENTATION EFFECT | ||
| The first substituent (G) may direct the next incoming group (E+) to ortho, meta or para position, depending on the nature of the first substituent. This is called directive or orientation effect. | ||
ACTIVITY EFFECT | ||
| The substituent already present may activate or deactivate the benzene ring towards further substitution. These effects are called the activity effects. | ||
DIRECTIVE EFFECTS OF SUBSTITUENTS | ||
| In monosubstituted benzene, C6H5-G, there are five hydrogen atoms. Ortho = 2 positions Meta = 2 positions Para = 1 position But, this distribution is never obtained. The products formed, in fact, is determined by the nature of the first substituent already present on the ring. | ||
