1) Why does polysubstitution frequently occur with Friedel-Crafts alkylation but not with Friedel-Crafts acylation?2) If Benzene is reacted with t-butyl chloride, why is the chief disubstituted product the para rather than ortho isomer?

See explanation

Explanation:

Friedel-Crafts alkylation frequently undergo polysubstitution because the process  leads to the addition of an electron donating alkyl group, which activates the benzene ring to further alkylation. The acyl group rather deactivates the ring towards electrophilic substitution.

When benzene is reacted with t-butyl chloride, the chief disubstituted product is the para rather than ortho isomer because the increased bulk of the tert-butyl group hinders attack at the ortho-sites.

explanation:

venn diagram is pictorial representation with of circles showing the relation between two finite sets or things. the intersection part of two circles conveys the relation present in between those sets or things.

here in the venn diagram of sand and salt two circles represent sand and salt. but the area falling under the intersection of these circle represents the mixture of sand and salt.

so, in a venn diagram the mixture will be placed in a middle that is in between the intersection of two circles.