CHEM 2211 1st Edition Lecture 23 Outline of Last Lecture I Stereochemistry of alkenes reactions Outline of Current Lecture I Nomenclature of alkynes II Reactions of alkynes Current Lecture the nomenclature for alkynes is the same as for alkanes and alkenes the only difference is the suffix at the end We replace ane with yne Other than that the same rules apply for naming systematically The longest continuous chain containing the carbon carbon triple bond is numbered in the direction that give the functional group suffix as low a number as possible If there is more than one functional group alkyne then the yne suffix gets a di tri etc in front of it If there is a alkene and an alkyne bond o Find the longest continuous chain with both functional groups o Number whichever way produces the lowest numbers on the functional groups without concern to which functional group gets the lower number o Then name the chain with the alkene number and chain length then alkyne number and suffix such as 1 hepten 5 yne o If the same low number is obtained in both directions go in the direction that gives the double bond the lower number Reactions of alkynes 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 The addition of hydrogen halides and the addition of halogens to an alkynes Adding a hydrogen halide produces a alkene Therefore a second reaction can occur if there is excess hydrogen halide The product of the second addition is a germinal dihalide o Germinal dihalide a molecule with two halogens on the same carbon Examples Cl Cl CH3C CCH3 HCl CH3C CHCH3 HCl CH3CCH2CH3 Cl The addition of water to an alkyne Alkynes undergo the acid catalyzed addition of water Water wont react without the presence of an acid H2SO4 Product formed is an enol The enol rearranges into a ketone Example H2SO4 OH O CH3CH2C CH H2O CH3CH2C CH2 CH3CH2C CH3 An enol a ketone A ketone and its corresponding enol are called keto enol tautomers Tautomers are constitutional ismoers that are in rapid equilibrium
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