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.

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.