Hydrogen halides electrophilic addition, alkynes

FIGURE 9 5 (a) Curved arrow notation and (b) transition state for electrophilic addition of a hydrogen halide HXto an alkyne... [Pg.378]

The most reactive alkenes in electrophilic addition are the most thermodynamically stable. This is because they also have the lowest activation energy when forming carbocations. Hydrogen halides add to alkynes in nearly the same way they add to alkenes. [Pg.37]

MECHANISM FOR ELECTROPHILIC ADDITION OF A HYDROGEN HALIDE TO AN ALKYNE... [Pg.309]

When formulating a mechanism for the reaction of alkynes with hydrogen halides we could propose a process analogous to that of electrophilic addition to alkenes m which the first step is formation of a carbocation and is rate determining The second step according to such a mechanism would be nucleophilic capture of the carbocation by a halide ion... [Pg.377]

Evidence from a variety of sources however indicates that alkenyl cations (also called vinylic cations) are much less stable than simple alkyl cations and their involve ment m these additions has been questioned Eor example although electrophilic addi tion of hydrogen halides to alkynes occurs more slowly than the corresponding additions... [Pg.377]

Furthermore kinetic studies reveal that electrophilic addition of hydrogen halides to alkynes follows a rate law that is third order overall and second order in hydrogen halide... [Pg.378]

Electrophilic addition to terminal alkynes (unsymmetrical) is regioselective and follows Markovnikov s rule. Hydrogen halides can be added to alkynes just like alkenes, to form first the vinyl halide, and then the geminal alkyl dihalide. The addition of HX to an alkyne can be stopped after the first... [Pg.201]

Hydrohalogenation (Section 10.9) An electrophilic addition of hydrogen halide (HX) to an alkene or alkyne. [Pg.1203]

Alkynes undergo electrophilic addition reactions with hydrogen halides and bromine, but these reactions have limited synthetic utility. However, one reaction of alkynes that is commonly used in organic chemistry is hydration of the carbon-carbon triple bond to give a ketone, a transformation that is catalyzed by mercuric ion in the presence of sulfuric acid (Eq. 11.10). [Pg.410]

Alkynes undergo many of the same electrophilic additions as alkenes. A characteristic reaction is a 7t bond acting as a nucleophile to make a new bond with an electrophile. In this section, we study the addition of bromine and chlorine as well as the addition of hydrogen halides. [Pg.314]

Electrophilic Addition of Hydrogen Halides to Alkenes and Alkynes... [Pg.548]

ELECTROPHILIC ADDITION OF HYDROGEN HALIDES TO ALKENES AND ALKYNES... [Pg.549]

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...