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SCAN0010 - Vi&\ACLQ so $31430 PEA VI Alkyne Preparation...

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Unformatted text preview: Vi \& \ACLQ? so $31430 PEA VI. Alkyne Preparation 3&3: (3 “925;: —; ilk/u “a“ MKJCTWW a2 Allgglation at acetylene and terminal aligns (acemlide anion alkylationz (read Ch. 9. 6) /‘\ _ 1. Na+NH2 . 1 Na+NH2- HC—‘CH ———-—> R—CZCH ——> R—C:—C'—R O 2. R-X‘ » ‘9 2. R-X 1 th&£ WW W disubstituted X= Cl, r, l monosubstituted acetylene acetylene O - . $.30 st e Alkylation involves a sequence of two separate operations: W (965 1. acetylene is converted to its conjugate base by reaction with sodium amide. : J" m Wk}: A ’W HC=_____C-—H Na+NH2' “—“—>‘ HCZC'Na+ + NH3 sodium acetylide 2. alkyl halide is added to the solution of sodium acetylide. The reaction i nucleophilic substitutio (The alkylating agent is an alkyl halide; The nucleophile is sodium acetylidei H—czc—R + :X' sodium acetylide may be also used. Limitation: Efiective only wit primary alk l halides. ( undergo elimination. E 2 predomina es over ‘N /‘ . \wa b Elimination o vicinal and jeminal dihalides or vin halfiad Ch. 9. 7) K. 313 . Ck \, ‘ V U A“ . (Y‘ yrs {flail — The most frequent applications are in preparation of terminal alkynes. i £1339“ l A? U; K (CH ) CCH CHCI NaNHz’ ”Ha (CH ) CCHfiCHCl NaNHz’ NH3 2 3 3 2— 2 3 3 — " U' _ - 9V” b geminal dihalide slow slow ’7” MD )q/fl WC)" 7.’\ KW N NH NH VON ’3ng (2:1) (CH3)aCC E CNa #4— (CH3)300 E CH fast L “20 i 3 equivalents of bases are needed. Wh ? (CH3)2CHCHCHzBr 1' Name A 2. H20 r vicinal dihalide NH3 (CH3)2CHCECH ...
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