Which of the following alkene addition reactions occur(s) specifically in syn fashion? A) dihydroxylation using OsO₄, H₂O₂ B) addition of H₂ C) hydroboration, oxidation D) addition of HCl E) A, B, and C

Question

Quizplus · Accepted Answer

Dihydroxylation using osmium tetroxide (OsO4), hydroboration-oxidation, and the addition of hydrogen sulfide (H2S) proceed via a syn addition mechanism. This means that the added groups attach to the same side of the double bond in the alkene. Dihydroxylation with OsO4 forms a cyclic osmate ester intermediate, leading to syn addition of hydroxyl groups. Hydroboration-oxidation involves the syn addition of a boron atom and a hydrogen atom across the double bond, followed by oxidation to give an alcohol. The addition of H2S does not specifically proceed in a syn fashion in general organic chemistry, but it is less commonly discussed in the context of syn or anti addition compared to the other reactions listed. However, the inclusion of H2S in option E may be an error, as its addition mechanism is not typically characterized as syn in standard organic chemistry texts. The correct and most accurate answer focusing on well-established syn addition reactions would be dihydroxylation and hydroboration-oxidation, making the inclusion of H2S questionable. The addition of HCl proceeds via an anti-Markovnikov or Markovnikov mechanism, depending on conditions, but is not specifically syn.

Which of the Following Alkene Addition Reactions Occur(s) Specifically in Syn