Mircea Darabantu
Mircea Darabantu
Mircea Darabantu
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<strong>Mircea</strong> <strong>Darabantu</strong> CHIMIE ORGANICA an II Ing. CURS-VII Pag.<br />
EXEMPLE:<br />
Regioselectivitati totale doar la formarea legaturilor duble unde nu exista alta optiune:<br />
H2SO4 95%<br />
170<br />
CH3-CH2-OH H2C=CH2 o H2SO4 20%<br />
CH3 C<br />
85 - 90<br />
H3C OH<br />
CH3 o C<br />
H3C CH2 H3C Tertbutanol Izobutena<br />
Produs exclusiv<br />
Regioselectivitati partiale la formarea legaturii duble:<br />
Deshidratare cu izomerizarea partiala (sau chiar completa) a carbocationului intermediar (primar → secundar) ca in<br />
cazul compusilor halogenati, prin acelasi mecanism E-1:<br />
H2SO4 75%<br />
CH<br />
140<br />
3-CH2-CH2-CH2OH CH3-CH2-HC=CH2 + CH3-HC=CH-CH3 oC n-Butanol 1-Butena (E si Z)-2-Butena<br />
Minoritar MAJORITAR (Zaitev)<br />
+ H + - H<br />
, - H2O +<br />
- H +<br />
CH 3-CH 2-CH 2-CH 2 +<br />
H: - transfer ion hidrura<br />
intramolecular<br />
CH 3-CH 2-C + H-CH 3<br />
(CH3) 3C-CH-CH3 (CH3) 3C-CH=CH2 + H2C=C(CH3)-CH(CH3) 2 + (CH3) 2C=C(CH3) 2<br />
OH<br />
3,3-Dimetil-2-butanol<br />
+ H + 3,3-Dimetil-1-butena 2,3-Dimetil-1-butena 2,3-Dimetil-2-butena<br />
LIPSA Minoritar MAJORITAR (Zaitev)<br />
, - H2O - H +<br />
- H +<br />
H3CCCH + CH3 -CH3 CH 3<br />
CH 3<br />
H 3CC + CH-CH 3<br />
CH 3<br />
8
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