{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

SCAN0012 - LHRQ‘E WOW W(1 electron transfer Transfer of...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: LHRQ‘E WOW W (1) electron transfer - Transfer of an electron from the metal to the alkyne to give an anion radical. 0 (1A . T. RCZCR‘ +M+ anion radical metal ion (2) proton transfer— Transfer of a proton fiom the solvent (liquid ammonia) to the anion radical @R RCZCR' + [\Hale RCZCHR' + :NH2 W ammoma alkenyl radlcal amlde Inn (3) electron transfer - Transfer of an electron from the metal to the alkenyl radical to give a carbanion. REZCHR' + ‘M RCZCHR' +M+ alkenyl radical alkenyl anion metal ion (4) proton transfer— Transfer of a proton from the solvent (liquid ammonia) to the earbanion . RCZCHR' + H~NH2 ——> RCH=CHR' + u :N alkenyl anion ammonia trans alkene amide Ion e Howl (13(06005 Problem: Suggest efiicient syntheses of (E)- and (3-2- heptene from propyne and any necessary organic or inorganic reagents. /\. [@mfi Electophilic @1101 to alkyne (hydrohalogenation) “Aims are s 1ghtly less reactive than alkenes Hydrogen halides add to alkynes to form alkenyl halides. RCECR' + HX RHC:CR' | x alkenyl halides Regioselectivity of addition according to Markovnikov's rule. Exception: HBr (but not HCl and HI) 1n the presence of peroxide adds to alkyne by a fiee radical mechanism A regioselectivity opposite to Markovnikov 5 rule 15 observed. peroxide CH3(CHZ)SCECH + HBr CH3(CH2)3CH:CHBr c) Addition of X2 (halogenation) , Addition of 1 mole of chlorine or bromine to an alkyne yields a trans dihaloalkene- A tetrahalide lS ¥j>€ formed on addition of a second equivalent of the halogen. /’\ ...
View Full Document

{[ snackBarMessage ]}