When alkynes are reacted with water, aldehydes and ketones are formed. While internal alkynes can only be converted to ketones by acid-catalyzed hydration or oxymercuration-demercuration, terminal alkynes can also be converted to aldehydes via anti-Markovnikov addition of hydroboration-oxidation: … Read more
Alkynes can be converted into carboxylic acids by ozonolysis. For external alkynes, the ozonolysis results in a carboxylic acid and carbon dioxide: The ozonolysis of internal alkynes, on the other hand, produces two carboxylic acids: In the reaction above, … Read more
Alkynes to Ketones Alkynes can be converted to aldehydes and ketones via hydration reactions such as 1) Acid-Catalyzed Hydration, 2) Oxymercuration-Demercuration, and 3) Hydroboration-Oxidation. The first two are used for Markovnikov conversion of terminal alkynes to ketones, whereas the hydroboration-oxidation … Read more
In the initial discussion about electrophilic additions to alkynes, we saw that in many ways, these reactions are similar to those of alkenes. For example, in hydrohalogenation reactions, both alkenes and alkynes are first protonated forming carbocation intermediates which are … Read more
In the introductory post about electrophilic addition reactions to alkenes, we emphasized that they are electron-rich species because of the two extra electrons brought in by the π bond. This feature makes them the nucleophile, or Lewis base in a … Read more
This is a summary practice problem of Alkyne reactions including the key reactions such as: Hydrohalogenation Halogenation Acid-Catalyzed hydration Hydroboration-Oxidation Ozonolysis Reduction to alkanes Reduction to cis and trans alkenes and others.
The first practice problem is a summary of alkyne reactions, followed by comprehensive synthesis practice problems; all the major classes of alkyne and alkene reactions are covered!These include the preparation of dialkyl halides and their use in the preparation of … Read more
Alkylation of Terminal Alkynes Many reactions of alkynes are similar to those of alkenes, as they are both π-bond systems that are capable of doing electrophilic addition reactions. One important difference is the acidity of the alkyne proton. The pKa … Read more
Ozonolysis of Alkynes The Ozonolysis is an Oxidative Cleavage reaction where both the π and σ bonds of the double or triple bond are broken to form two carbonyl groups. If you remember, in the case of alkenes, either ketones … Read more
Hydroboration-Oxidation of Alkynes Like alkenes, alkynes can also be subjected to Hydroboration-Oxidation to achieve an anti-Markovnikov addition of an OH group to the π bond. As in the case of acid-catalyzed hydration and oxymercuration, the intermediate here is an enol, which, this … Read more
