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Updated: May 20, 2026

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
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Published on: February 24, 2015

Continuous-flow synthesis of monoarylated acetaldehydes using aryldiazonium salts

Natalia Chernyak1, Stephen L Buchwald

  • 1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

Journal of the American Chemical Society
|July 21, 2012
PubMed

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In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
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The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.