Question

Under what conditions would this reaction occur? What is the solvent?

کا سر (5 5)

Answer 1

Alkynide Anion Formation

First, the terminal alkyne must be deprotonated with a strong base, such as sodium amide (NaNH2). This proton can be removed because terminal alkyne hydrogens are more “acidic” than alkene or alkane hydrogens. This forms the alkynide anion, which is a great nuleophile. This neucleophile formation is favored by using strong bases like ammonia as solvent. Solvent choice plays an important role here and we must choose basic solvent that is less acidic than alkyne C-H, so that the formed anion stays stable to react with alkyl halide.

Next, the a alkynide anion must attack a primary or secondary carbon center to perform an SN2 type reaction. This displaces the leaving group and forms the new C-C triple bond, which has now become an internal alkyne. Here is the reaction scheme.

H3 Nanfz Alky nes have audie CEC-H bond whicn Can be defatonate in ta rescna Strong oae ike NH2 Camda anion Here amonia is 3hrangar base taa algn SD,e reactim ets driven Na Na NH 2 ti alkynide readily ypercactron rwrd alkynideanion rea s alkyk halides în S2 -ć Solveuts aric sotvents Such as ammonia actasgnd Solvents becauye tay Stabilge alkywide anism allrsí n nisn alocsi Sn2tren