Provide explanations for the following observations a The addition of HCl to A is ca 3000 x faster than with B Use words and structural drawings to support your answer HCl O O A Cl C racemic B Possible Carbocationic Intermediates for hydrohalogenation O O Aint2 Aint2 O Aint1 secondary carbocation destabilized by electron withdrawing group EWG Bint secondary carbocation Cyclohexylcation Bint is much less stable higher in E and therefore is more difficult to form than the resonance stabilized cation Aint2 secondary resonance stabilized carbocation the most stable b An optically active sample of C reacts witha solution of sodium acetate to give an optically active product D while the combination of the same optically active C with a solution of acetic acid gives D as an optically inactive racemic mixture O Why does the reaction of C with acetic acid give racemic product while the H D What is the structure H C O Na reaction with sodium acetate does not 3 Cl O Use words to explain and then draw the C mechanism for formation of racemic D D O Sodium Acetate is a good nucleophile anionic and favors SN2 mechanism no ionization O H HOAc O H Cl O H solvolysis O Cl trigonal planar C achiral intermediate must lead to racemic product O O O H CH3 HO O H O H O CH3 HO You could also use the other oxygen atom of acetic acid as the nucleophile O O H O O H O CH3 O The deprotonation of phenylacetonitrile E can be performed with sodium hydride NaH in an appropriate solvent Using curved arrow notation draw a mechanism for the following deprotonation mechanism H is base deprotonates phenylacetonitrile H H C E N Na H H Na C DMSO F N H2 When phenylacetonitrile 1 4 dibromobutane and an excess of NaH are combined in DMSO the following product was observed J Org Chem 1994 59 6464 Starting with the conjugate base of phenylacetonitrile F draw the mechanism for the formation of the observed product This reaction occurs by more than one step so be sure to draw each intermediate Don t forget that excess NaH is available as needed H H C N Br Br excess Na H C DMSO N 2H2 2NaBr G E Na H C Br Br SN2 C N F C NaBr N intramolecular SN2 excess Na H Br H NaBr N acid base rxn Br Na H2 C N G Nitrile G can be converted into toslylate H recall that TsO stands for tosylate and that tosylates are good leaving groups Upon warming tosylate H in CF3CH2OH a carbocation is generated draw the structure of this cation and then draw arrows showing how this cation is converted into I and J CH OTs CH3 CH3 CH3 G I H C CH3 J H C CH3 H C CH3 Using reactions that you know and any required reagents convert propyne to racemic 2R 3R 2 3 dichlorononane CH3 1 NaNH2 Na NH3 CH3 H3C CH3 Br DMSO NaBr H3C H3C CH3 H3C H3C Cl Cl Cl R Cl R CH3 H2 gas Lindlar catalyst Cl2 CH3
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