CHE-2201 Lecture Notes - Lecture 10: Markovnikov'S Rule, Locant, Alkyne
Document Summary
Incorporate a c-c triple bond (short and strong) Assign locant to each substituent giving the c-c triple bond the lowest. List numbered substituents before parent name in alphabetical order. The c-c triple bond locant is placed either just before the parent name or just before the -yne suffix. Terminal: at the end of a molecule. Internal: in the middle of a molecule. Terminal alkynes have a lower pka than other hydrocarbons 1019 times stronger than ethylene. Because acetylene is still much weaker than water (pka = 15. 7), a strong base is needed to make it react, and water cannot be used as the solvent. A bases conjugate acid pka must be > 25 for it to be able to deprotonate a terminal alkyne. Often, excess equivalents of nanh2 are used to shift the equilibrium toward the elimination products. A proton source is needed to produce the alkyne. Two equivalents of h2 are consumed for each alkyne alkane conversion.
