Which option correctly matches the four main types of organic reactions with their basic descriptions?

Which option correctly matches the four main types of organic reactions with their basic descriptions?

• A. Addition eliminates atoms; Substitution reorganizes the skeleton; Elimination adds functional groups; Rearrangement reduces oxidation state.
• B. Addition adds atoms to unsaturated bonds; Substitution replaces an atom/group; Elimination removes atoms forming a double or triple bond; Rearrangement reorganizes the carbon skeleton.
• C. Addition forms salts; Substitution hydrolyzes water; Elimination polymerizes; Rearrangement removes oxygen.
• D. Addition replaces atoms; Substitution forms multiple bonds; Elimination adds atoms; Rearrangement creates new functional groups.

Answer: (B)

Understanding these four broad classes of organic reactions helps organize how molecules transform. Addition adds atoms to unsaturated bonds such as alkenes or alkynes, seen when a reagent adds across a double or triple bond, like HCl adding to an alkene to give an alkyl halide. Substitution replaces an atom or a group with another, such as a halogen replacing a hydrogen or a hydroxyl group being substituted by a nucleophile. Elimination removes atoms to form a multiple bond, such as dehydration of an alcohol to give an alkene or dehydrohalogenation to give an alkyne. Rearrangement reorganizes the carbon skeleton, moving atoms within the molecule to create a different arrangement or a more stable structure, as in carbocation hydride or alkyl shifts. This description matches the four main types with their standard effects, making it the best choice. Other options mix up these roles—for example, describing addition as eliminating atoms, or giving substitutions as hydrolyzing water or forming salts, or claiming rearrangements remove oxygen—so they don’t align with how these reaction classes are actually defined.

Understanding these four broad classes of organic reactions helps organize how molecules transform. Addition adds atoms to unsaturated bonds such as alkenes or alkynes, seen when a reagent adds across a double or triple bond, like HCl adding to an alkene to give an alkyl halide. Substitution replaces an atom or a group with another, such as a halogen replacing a hydrogen or a hydroxyl group being substituted by a nucleophile. Elimination removes atoms to form a multiple bond, such as dehydration of an alcohol to give an alkene or dehydrohalogenation to give an alkyne. Rearrangement reorganizes the carbon skeleton, moving atoms within the molecule to create a different arrangement or a more stable structure, as in carbocation hydride or alkyl shifts.

This description matches the four main types with their standard effects, making it the best choice. Other options mix up these roles—for example, describing addition as eliminating atoms, or giving substitutions as hydrolyzing water or forming salts, or claiming rearrangements remove oxygen—so they don’t align with how these reaction classes are actually defined.