CHEM 3331 1nd Edition Lecture 15Outline of Last Lecture I. Nucleophiles for Sn2II. Substrates and leaving groups for Sn2III. StereochemistryIV. Sn1 reactionV. RearrangementsVI. Sn1 vs. Sn2Outline of Current Lecture I. E1 reactionII. Zaitsevs RuleIII. E2 reactionIV. StereochemistryV. E1 vs. E2 vs. Sn1 vs. Sn2Current LectureI. E1 reactionE1 reaction is an elimination reaction which removes a smaller molecule from a largere molecue. This reaction creates alkenes. CH3CH2Br + OH- CH3CH2OH + H2C=CH2C(CH3)3Br (-Br-) C(+)(CH3)3(Sn1)+CH30H C(CH3)3O(+)HCH3Or E1 C(=CH2)(CH3)2 + H+C(+)CH3CH3CH2H (ACID) + CH3OH (BASE) CH3O(+)H2 + C(=CH2)(CH3)2You can look at E1 as an acid base reaction. It shifted one H+ from one molecule to another.Rate=k[“acid”]. Weak bases are ok. The reaction proceeds to carbocations.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Zaitsev’s RuleC(CH3)2ClCH(CH3CH2)2(-Cl-) C(+)(CH2-H)2C-H(CH3CH2)2C(=CH2)CH3CH(CH3CH2)2 OR (CH3)2C=C(CH3CH2)2There is more of the second compound. R2C=CR2 > R2C=CRH > RHC=CRH AND R2C=CH2 > RHC=CH2 R= carbon based groupTetrasubstitutedtrisub disub monosub.It uses the principle of hyperconjugation. The more alkyl groups there are the more stable the compound is.III. E2 reactionIt is a single step reaction. HCH2CH2Cl +OH- H2C=CH2 +H20+Cl-HCH2C(CH3)2Br +OH- H2C=C(CH3)2 +H2O+ Br-This reaction requires a strong base, weaker acid, and no carbocation is made. The strong base is attracted to small periphery atoms such as H+It works best for tertiary>secondary>primary. Tertiary contains more alkyl groups which makes the moeule more stable.IV. StereochemistryE1 vs. E2 vs. Sn1 vs. Sn2NucleophileGood nucleophile and weak base (I-, PR3) Sn2 if substrate is primary or secondary Sn1 if substrate is secondary or teriaryWeak nucleophile and weak base (H2O, ROH) Sn1 if substrate is secondary or tertiary E1 is substrate is secondary or tertiary(minor)Good nucleophile and strong base (OH-) Sn2 and E2Primary: 91%:9%Secondary: depends usually close to half eachTertiary: only E2Weak nucleophile and strong base(Potassium tertiary butyl, LBA)E2 and Sn285%:15%SubstratePrimaryAnd strong nucleophileSn2And strong base E2And weak nucleophile no reactionSecondaryAnd good nucleophile Sn2And strong bulky base E2And weak base E1 and Sn1TertiaryAnd strong base E2And weak base Sn1 and
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