The Diels Alder reaction is a concerted reaction, which means Group of answer choices The product contains a cyclic ring. The diene must be in the s-cis conformation to react. Both exo and endo products are formed. It is an endothermic reaction. All changes in bonding (bond making and bond breaking) occur simultaneously.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.