Question

Open Question Point 10 HUST-Orgehem Discussion It was observed that imine and enamine formation are slow at both high pH and low pH but reach a maximum rate at a weekly acidic pH around 4 to 5. Explain. Reaction rate 1 2 3 4 5 6 7 8 pH pH dependence of imine and enamine formation Answer 19

Answer 1

a @Aldehydes I ketones react wilt number 아 ammonia derivative to form imine & enamine. Ketones real wilk amine derivative ale (NH₂-2) reaction mechanism. OH Ht -R primary amine following 애 ön (ritza? R R R carbino amure) z R-C=N-2 -ht 0₂ R-C NH R-C = NH-2 above a good leanny grunt ot arid is not mechanism, it is requied to protonale Gabinolamine unler mediale so that for can become enough present (ie medium is is highly basie on the other hand, it enough iu present (i medium is aridie hanning low pH), completely protonated hamy high pH), the reaction will be slow. arid then Nhz-z is & reaction can not occur. -2 NH₂-2 H H At 1 PH = 4.5 At this pH does not take place reaction rate is maximum. complete protonation of amine . Ht is present to Further at this pH, enough facilitate dehydration dehydration step.

one In aldol of aldehyde way Londensation addition of mole mile yde (or ketone) to a second molemle occus in the such a that X-Carbon is attached to the of Ist molenie carbonyl Carbon 2nd molecule. haree for aldol condensation, molenie have X-Carbon. & this a-carbon must contain hydrogen (ri X-hydrogen). hydrogen is attached to sp3 hybridised carbon. of the d CH3 6 (th -c-C-H do not have a hydrogen Ниш В2 ) do not aldol condensstion, Halo form neaction & Kelones which undergo given by those aldehydes contains (ohne & ahohols containing congren - 애 group group с : CHO not have coyne-grop. These grup. These compounds can undeys to do form (ie halo form) reaction Stability of an and depends on the stability of its anion Rad - on tHt R. anion and Greener anion more aridic is the compound a sility of

į 01) c-oh THt In this anion, negative charge ( due to removal of out) on o is stable as oxygen and most electionegative by element. Further it is stabliseo resonance erito th-cn (ii) CH-C-H Н fet Though OW carbon is " he 1 stablised by resonance but it is present on Carbon which is thaw ani هے electio negative oxygen. chyněcom-Econ Com a cena coz thit we have a extended resonance & after resonance sunce gader of stability of anion! > Chan & En- & -cry > tere change comes on ongen atom. c=0 į order of aridhi character I > I > I