【正文】 oC , 1 a t m )P dH 2Synthesis of alkanes and cycloalkanes +e t h y l a c e t a t e2 H 2O O5 C y c l o n o n y o n eC y c l o n o a n o n eP dSynthesis of alkanes and cycloalkanes B: Reduction of Alkyl Halides General Reaction: Zinc atoms transfer electrons to carbon atom of alkyl halide: R XZ n , H X( Z n X 2 )R HR Z n 2 + X Synthesis of alkanes and cycloalkanes Specific Examples 2 C H 3 C H 2 C H C H 3B rZ nH B r2 C H 3 C H 2 C H C H 3H+ Z n B r 22 C H 3 C H C H 2 C H 2 B rZ nH B r+ Z n B r 2C H 3 C H 32 C H 3 C H C H 2 C H 3Synthesis of alkanes and cycloalkanes Alyklation of terminal alkynes General reaction Specific reaction C CR HN a N H 2C C N a +R +R 39。t e r m i n a l a l k y n e s o d i u m a m i d e a l k y n i d e a n i o n R 39。 SR S R 39。 OR O R 39。 C C C C R 39。 C OOR O C R 39。 NR N R339。 s r u l em o r e s t a b l e a l k e n ek i n e t i c c o n t r o lH o f m a n n r u l eB : C H3C H2O: m a j o r p r o d u c t i s aB : ( C H3)3C O: m a j o r p r o d u c t i s bThe stereochemistry of E2 Reactions C CHLB :A n t i p e r i p l a n a rt r a n s i t i o n s t a t e( p r e f e r r e d )C CHB :LS y n p e r i p l a n a rt r a n s i t i o n s t a t e( o n l y w i t h c e r t a i n r i g i d m o l e c u l e s )E2 Elimination where there are two axial cyclohexane βHydrogens HC H ( C H3)2HC lHHH3C( a )C H ( C H3)2H3C1 M e n t h e n e ( 7 8 % )( m o r e s t a b l e a l k e n e )( b ) C H ( C H3)2H3C2 M e n t h e n e ( 2 2 % )( L e s s s t a b l e a l k e n e )E t O( a )E t O( b )C H ( C H 3 ) 2C lH 3 C C H ( C H 3 ) 2C lH 3 CN e o m e n t y l c h l o r i d e M e n t h y l c h l o r i d eE2 Elimination where only Eligible axial cyclohexane βHydrogen is from a less stable conformer HC H ( C H 3 ) 2C lHHHH 3 CM e n t h y l c h l o r i d e( m o r e s t a b l e c o n f o r m a t i o n )HC H ( C H 3 ) 2C lHHHC H 3E t OH 3 C C H ( C H3 ) 2L e s s s t a b l e c o n f o r m a t i o nE l i m i n a t i o n i s i m p o s s i b l e2 M e n t h e n e ( 1 0 0 % )Dehydration of Alcohols General reaction: The relative ease of dehydration is in the following order C CO HH Ah e a t+ H 2 OCRRRO H CRRHO H CHRHO HAcidcatalyzed dehydration of secondary or tertiary alcohols: An E1 reaction C CROH R 39。HHC CRO+H R 39。C C+RH R 39。+ H ADehydration of primary alcohol: An E 2 reaction C CHOH HHH + Af a s tC CHO+H HHHC CHH HA+s l o wC CHH+ H A+ AO+HHRearrangements during dehydration of secondary alcohols CHCC H 3H 3 C C H 3C H 3 O HC CC H 3H 3 CC H 3C H 38 5 % H 3 P O 4h e a t+ C CHC H 3H 2 CC H 3C H 3m a j o r m i n o rRearrangements during dehydration of secondary alcohols CHCC H3H3C C H3C H3O H+H O+HHCHCC H3H3C C H3C H3+O H2CHCC H3H3C C H3C H3+O H2C CHC H3H3C C H3C H3+C CHC H3H3C C H3C H3+2o C a r b o c a t i o n l e s s s t a b l eC CH2CH3C C H3C H3δ +δ +t r a n s i t i o n s t a t e1 , 2 s h i f tC CHC H3H3C C H3C H3+3oc a r b o c a t i o nm o r e s t a b l eC CC H3CH2C H3C H3+A :HHabC CC H3H3CC H3C H3+ C CHC H3H2CC H3C H3m a j o rm i n o rRearrangements during dehydration of secondary alcohols C H3C H3O HH+ h e a t H2OHCC H3C H3+C +C H3C H3+C H3C H3H+ H+C H3C H3Alkenes by debromination of vicinal dibromides C CB r B r+ 2 N a I + I 2C CB r B r+ + Z n B r 2a c e t o nC H 3 C O 2 HZ nSynthesis of alkynes by Elimination Reactions C CHRHRB r B r+ R C C R + 2 N H 3 + 2 B r 2 N H 2 H 2 C C H C H 2 C H 3B r 2C C l 4C H 2 B r C H B r C H 2 C H 3N a N H 2m i n e r a l o i l1 1 0 1 6 0oCH C C C H 2 C H 3Synthesis of alkynes by Elimination Reactions OC H 3C lC H 3C lP C l 51 . N a N H 22 . H +C HHydrogenation of alkynes Syn addition: Anti addition: H 3 C C C C H 3 P tH2H 3 C H C C H C H 3 P tH2 C H 3 C H 2 C H 2 C H 3H 3 C H 2 C C C C H 2 C H 3H 2 / N i 2 B ( P 2 )( S y n a d d i t o n ) C CC H 2 C H 3H 3 C H 2 CH HC CH 2 , P d / C a C O 3L i n d l a r 39。r a d i c a l m e c h a n i s mThe sterochemistry of the reaction C H 2HCC 2 H 5H XC 2 H 5 CCH 2H+H+ XC 2 H 5XHC H 3( S ) C 2 H 5HC H 3H5 0 %( R ) 5 0 %r a c m i c f o r mStereochemistry of the addition of halogens to alkenes HB r 2 ( b )HB r+B r ( a )HB rHB rB rHB rH( b )( a )Halohydrin formation C C H2H3CH3CB r2C C H2C H3H3CB r++O H2C C H2B rC H3H3CO+H2H+C C H2B rC H3H3CO H7 3 %Divalent carbon pounds: Carbens C CH RR H+ : C C l 2 C CH RR HCC l C lT h e a d d i t i o n o f c a n b e n e s i s s t e r o s p e c i f i cC H 2 N 2K O C ( C H 3 ) 3 / C H C l 3C H 2 I 2 / Z n ( C u ): C H 2: C C l 2: C H 2Oxidation of alkenes: syn hydroxylation. + M n O 4H HO OM nOOH2OO H c o l d H HO H O HC i s + O s O 4H HO OO sOON a H S O3H2O2 5oC H HO H