Why Friedel–Crafts alkylations often give polysubstitution products but Friedel–Crafts acylations do not.

Alkyls groups are electron donating hence activating benzene ring for further alkylation as result polysubstituted product is obtained. While acyl groups are electron withdrawing and ring deactivating as result further substitution does not take place

Write the Dehydration and ring expansion mechanism of following alcohol:

This reaction proceed via carbocation  intermediate  formation and ring expansion in which  a molecule of water is lost in presence of concentrate Sulphuric acid. The initially formed primary carbocation rearranges to more stable secondary carbocation which results in ring expansion.

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Explain Dehydration and ring expansion mechanism of 1-(1-Methylcyclopentyl)ethan-ol?
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Write Dehydration and ring expansion mechanism of 1-cyclobutylethanol in the presence of con H2SO4.

Write Dehydration and ring expansion mechanism of 1-cyclobutylethanol in the presence of con H2SO4.

Related Examples:
Explain Dehydration and ring expansion mechanism of 1-(1-Methylcyclopentyl)ethan-ol?
Explain the ring expansion mechanism of Bicyclic 1,2-Diols which undergoes pinacol pinacolone mechanism?

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Related Examples:
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Explain Dehydration and ring expansion mechanism of 1-(1-Methylcyclopentyl)ethan-ol?

Dehydration of 1-(1-Methylcyclopentyl)ethan-ol follow E1 Elimination Mechanism and take place in the presence  concentrate sulphuric acid: