lecture_01_chapter_13

lecture_01_chapter_13 - Lecture I, Chapter 13, Chem 308...

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Lecture I, Chapter 13, Chem 308 ORGANIC CHEMISTRY 308 LECTURE I CHAPTER 13 Welcome to Chemistry 308. Congratulations on being here. Alkynes: Continuing our survey of functional groups. 1. An alkyne is a hydrocarbon with a triple bond. A triple bond introduces two degrees of unsaturation. Therefore the general formula of a hydrocarbon with one triple bond is C n H 2n-2 . Notice that an alkyne is at a higher oxidation level than an alkene because it has two fewer hydrogens. 2. Nomenclature. Systematic is the same as alkenes but no cis, trans or EZ issues. Key points: main chain: If the triple bond is the only functional group, the main chain must contain the triple bond numbering priority: number from the end of the chain that gives the triple bond the lowest number. suffix “yne” denotes the carbon-carbon triple bond. Some other points a. acetylene is a widely used common name acceptable in the system. b. other alkynes can be given common names as substituted acetylenes (methylacetylene etc or diisopropyl acetylene as opposed to ?)) c. terminal vs internal. Important because of the H, as we shall see. d. The common name propargyl is used for the CH CCH 2 - radical. 1
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Lecture I, Chapter 13, Chem 308 e. Hydrocarbons that have both a double and a triple bond are named as enynes with a number indicating the location of each double and triple bond in the chain. The chain is numbered from the end that gives a multiple bond the lowest number. If there is a tie (and only if there is a tie) then the double bond has priority in numbering. When a hydrocarbon contains more than one unsaturated centre, the parent chain is chosen to contain the maximum number of unsaturated groups, even though it may be possible to designate a longer, but more saturated chain. For example 3-(3-methylbutyl)hex-4-en-1-yne f. All functional groups (except halides) take priority over unsaturated centers (alkenes and alkynes). These functional groups are called principal functional groups. The main carbon chain is chosen to include the maximum number of principal functional group, and is numbered to give the lowest possible number to a principal functional group first , before unsaturated centers are considered. For example OH 3-propargylhex-5-en-2-ol 2
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Lecture I, Chapter 13, Chem 308 3. Physical properties as expected for hydrocarbons. But alkynes tend to be relatively high boiling compared to alkenes mostly because of greater polarizability. Still the lower molecular weight alkynes are gases at room temperature. Also terminal alkynes tend to be higher boiling than internal ones because of the polarity of the C-H bond. 4. Structure. You can predict one σ bond and two π bonds based on what you know about orditals. a. With two electron groups (two bonds) the geometry is linear
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This note was uploaded on 06/25/2009 for the course CHEM 01:160:308 taught by Professor Bokiess during the Spring '09 term at Rutgers.

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lecture_01_chapter_13 - Lecture I, Chapter 13, Chem 308...

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