October 20 - aéotwme 24, &W so, 2008 Nomenclature of...

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Unformatted text preview: aéotwme 24, &W so, 2008 Nomenclature of alkenes Naming simple alkenes is... simple. Just replace the -ane ending of an alkane with -ene. propane becomes propene butane becomes butane But there are at least two possible butenesl 1-butene and 2-butene I When naming an alkene, we find the longest continuous carbon-carbon chain that includes the doubts bond. Then number the chain in the direction that gives the double bond the lowest number. \ S - I MM 0 this mo ecule I 3 b is 2-pentene, not 3-pentene lsomerism in aikenes gives rise to more possibiiities. W A \/’~H “xi/Lt. 1-butene 2-methylpropene cis—2—butene trans-Z-butene jigmemfiot. ,owa/ekmes woke/<5 cgofiag-W & ME’WWM me. Cowstt'. tot/to ism w-Li’g/ C4143 Naming stereoisomeric alkenes using Cahn-lngotd-Prelog rules Use the Cahn-lngold—Prelog priority rules to assign alkene geometry as either E or Z. When atoms of higher atomic number are on the same side of the double bond: When atoms of higher atomic number are on opposite sides of the double bond: First. understand what it means to be on the same or opposite sides of the double bond: (22> Naming stereoisomeric alkenes using Cahn-lngold—Prelog rules, continued Then assign priority to each group using Cahn-lngold-Prelog rules: Compare these Compare these two groups to two groups to each other each other #- H cr — Br j bid/a: : :F 06.10% cmgrw) ' ‘1': The higher priority groups are 0 the same side. so this is a Examples: (Note: The -OH group "outranks" the (£ ) "’ 3" E‘X/Q'VLQ— ) " .. atkene. Number the chain in the direction that gives the OH the lower iocant.) 2- me‘t’éjfi u i [email protected]'te:vr..e_.. 4/2. 5 JBr CE)» 3“33£oww-4— me zen 2W Relative stabiiities of isomeric aikenes Lower heat of combustion = more stable alkene Two maior factors: 1) degree of substitution: how many R groups attached to the aikene e LMAJVL £122.31: ‘ R R 2 "K R K H H H R \ x H \ / \ _ , x __ / R\c: / C=C/ C=C/ > ’0 :C > C__C > /C.._.C.\ C \ / \ / “ / \ / \ H H H H H K R a H H R H .. g; a «wee. ashamzs— RCH=CHE Rzequz 6L 2) van der Waals strain: R groups cis to one another are destabilizing ) tat/f R .56 M :06 4.4 Mas-fags. M g rifled/ts fl OLGA—‘3. fiend}; safacmmmvdai‘w) cam /6£. Meat, 'to- com/ome. «Le/eatith flih/Mffiw 4%? Mém. H2, A/ ——_———'--‘-__% 7;?Ks/ ?{:)B£)N{”Eh) H H CLO-urge, W P 01/ C “631’!” awab-M/ AID” H2 fir j 7?an N1: (3 _._.__ Q ’66 296315151 Mun/Le. 11me @eoukivwg, $32948 WW- LW JP‘ mm fiuzgrvtorL tit/fame.” z 3&6” ymfl§mfi smug. 0-H Jim/tats) R .v‘m A AH .-= ~26-9 howeer “fdgf’bé'y /k/ M H / MW / H }M=_28'5écfl’e 5 0- % Same, sandal-66m mo’e X/ M /l\/\ ,‘AH:—-—-3o.3’§m,e / H 1128 (San/v1.2» mm'tcm H ...
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This note was uploaded on 02/25/2010 for the course CHEM 3311 at Colorado.

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October 20 - aéotwme 24, &W so, 2008 Nomenclature of...

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