Basic IUPAC Nomenclature I - Organic Chemistry

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Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesBasic IUPAC Nomenclature IStraight Chain Alkanes Straight chain alkanes have only carbon and hydrogen atoms. Formula is CxH(2x 2) All the carbons in alkanes are sp3 hybridized and in straight chain alkanesall the carbons are linked in a straight line. (Exactly two ends) Straight chain alkanes are named for the number of carbons in the chain. All straight chain alkane names end in –ane; which shows that the onlyfunctional group present is alkanes.Basic Straight Chain Alkanes C1 - C10C1 methane CH4C2 ethaneCH4CH3CH3C3 propaneCH3CH2CH3C4 butaneCH3(CH2)2CH3C5 pentaneCH3(CH2)3CH3C6 hexaneCH3(CH2)4CH3C7 heptaneCH3(CH2)5CH3C8 octaneCH3(CH2)6CH3C9 nonaneCH3(CH2)7CH3C10 decaneCH3(CH2)8CH31

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesAdvanced Straight Chain Alkanes C11 – C20C11 undecaneCH3(CH2)9CH3C12 dodecaneCH3(CH2)10CH3C13 tridecaneCH3(CH2)11CH3C14 tetradecaneCH3(CH2)12CH3C15 pentadecaneCH3(CH2)13CH3C16 hexadecaneCH3(CH2)14CH3C17 heptadecaneCH3(CH2)15CH3C18 octadecaneCH3(CH2)16CH3C19 nonadecaneCH3(CH2)17CH3C20 icosaneCH3(CH2)18CH3Notes: With 5 or more carbons straight chain alkanes count generally usingGreek prefixes. Memorizing 1-10 is sufficient for 8A, students in 118A should know 120.2

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesBasic IUPAC Nomenclature IIAlkyl Groups You can make an alkane into an alkyl group by removing a hydrogen. Alkyl groups of straight chains are named by dropping the ending –aneand adding the ending –yl to the base name of the chain.HH C HHa methane molecule HH CHa methyl groupH HH C C HH Han ethane moleculeOnce we get to three or more carbons there are choices. We can formstraight chain or branched alkyl groups.H H HH C C CH H Ha propyl groupH H HH C C C HH H HH H HH C C C HHHa propane moleculean isopropyl groupa branched chainsubstituenta straight chain orn-alkyl substituent H HH C CH Han ethyl groupMany smaller branched alkyl groups get common names. These namesare old fashioned, but are still often used. The following common namesare in general use and should be remembered.isopropylisobutylsec-butyltert-butylH H HH C C C HHHH H HH C C CH C HHHHH H H HH C C C C HHH Hthe iso- prefix is included in alphabetizationXXthe sec- prefix is italicized and separatefrom the name and is NOT included inalphabetization.XHHHH CH C CH CHHHX3the iso- prefix is included in alphabetizationthe tert- prefix is italicized and separatefrom the name and is NOT included inalphabetization.

Lievens,University of California, Davis January 2012Chemistry 118 SeriesBranched alkyl groups can also be named by IUPAC by treating eachbranch as a substituent off the main chain. When naming branched alkylgroups using IUPAC the carbon attached to the point of interest (e.g. mainchain) is carbon one.methylCommonisopropylH H HH C C C HHHIUPAC211-methylethylXmethylisobutylH H HH C C CH C HHHHX2132-methylpropylmethylsec-butyltert-butylH H H HH C C C C HHH HHHHH CH C CH CHHH2131-methylpropylXmethyl1,1-dimethylethyl *12X* Unlikemost prefixes di-, tri-, tetra- etc prefixes in branched substituents counttowards alphabetical order. e.g., 1,1-Dimethylethyl rather than 1,1-diMethylethyl.Notes: Alkyl groups are generally substituents meaning they have a bondattached to something of note (e.g., halogens, amines, alcohols, ethers,longer chains). Alkyl groups are never complete molecules on their own. The variable –R represents any alkyl group. iso- groups generally have the form (CH3)2CH-X sec- groups attach via a secondary carbon tert- groups attach via a tertiary carbon4

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesBasic IUPAC Nomenclature IIIBranched Chain Alkanes/Haloalkanes Branched chain alkanes have only carbon and hydrogen atoms.haloalkanes have a halogen (F, Cl, Br, I) Formulas are CnH(2n 2) for alkanes or CnH(2n 2-y)Xy for haloalkanes All the carbons in alkanes are sp3 hybridized and in branched chainalkanes the chain forks. (More than two ends)IUPAC Nomenclature of branched alkanes follows these steps:1) Find the longest chain of continuous carbons. This is now the mainchain. Name this chain as if it were a straight chain alkane.a. If two chains are the same length choose the one with morebranches.2) Count the carbons in the main chain left to right and right to left. Thedirection you first run into a substituent is the direction use to numberthe chain.a. If the numbers are the same go to the next nearest substituentb. If the numbers are exactly the same regardless of direction thelower numbers go to the first substituent in alphabetical order.3) Give each substituent a number according to which carbon itʼsattached to.4) List the substituents in alphabetical order in front of the main chain.a. Branched substituents get parenthesis around themb. Numbers are separated from numbers by commasc. Numbers are separated from words by hyphens5) Multiple straight chain substituents of the same kind are combined andgiven a prefix to indicate the number (di-, tri-, tetra-). These prefixes donot count towards alphabetical order. If the substituent is branched(bis-, tris-, tetrakis-) are used.Notes: Sometimes it helps to think of each carbon in the main chain as a houseon a street. The substituents that live there each get an address (number)according to which house (carbon) they live at. Once youʼve found your main chain circling or labeling it can show youwhat you still have left to name as substituents To find the longest chain pick an end and follow it to the first branch. Makesure you have the longest end on that branch. Follow the chain to the nextbranch selecting the longest continuing chain each time you find a branchuntil you run out of molecule. F- is Fluoro, Cl- is Chloro, Br- is Bromo, I- is Iodo. They get no specialpriority 5

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesExamples:ClBrBrCompound BCompound AClBr1)Bran octanea nonaneWe could have started in the lower leftor ended in the upper right and gottenthe same length, but this chain has 5substituents rather than 3 or 4.2)We could start at the lower leftmethyl and the result would beexactly the same.Cl1 2Br34567876 5 489Left to right we get substituents atpositions 2,3,5,7,and 8Right to left we also get substituents atpostions 2,3,5,7, and 8.The first substituent L-- R is Chloro,the first substituent R-- L is Methyl.C comes first so L-- R is correct.3)32BrLeft to right we get substituents atpositions 2, 5, 6, and 7.Right to left we also get substituents atpostions 2,3,4, and 7.2 2 so we go on to the nextsubstituent and 3 5 so we use R-- LCl1 21Br345678876 5 43Br2192-bromo3-bromo4-isopropyl or e2-chloro-3,7-diethyl-5,8-methylnonane6

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesPractice Alkane and Haloalkane Nomenclature:ICompound ACompound BClBrClCompound CClBrCompound DClBrCompound ECompound FBrClFBrClCompound GCompound HCompound IBrClClBrCompound JCompound KCompound LClBr BrFCompound MBrBrCompound N7Compound O

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesPractice Alkane and Haloalkane Nomenclature Key:Compound A:2,2-dimethylhexaneCompound B:4-isopropyl-3,6-dimethyloctane or3,6-dimethyl-4-(1-methylethyl)octaneCompound C:4-ethyl-4-iodo-3,6-dimethyloctaneCompound D:6,7-dibromo-2,3-dichlorononaneCompound E:7-bromo-8-chloro-3,3-diethyldecaneCompound F;5-sec-butyl-3-chloro-6-ethyl-2-methylnonane neCompound G:2,3-dibromo-2,4,4-trimethylpentaneCompound H:5-ethyl-1-fluoro-6,6-dimethylheptaneCompound I:3,4-dichloro-7,8-dimethyldecaneCompound J:3-ethyl-2,6,7-trimethylnonaneCompound K:5-sec-butyl-2-chloro-6-isopropyldecane aneCompound L:6,7-dibromo-1-chloro-4-isobutyloctane pound M:2-chloro-3-fluorobutaneCompound N:2,2,3,3-tetrabromo-5,6-diethyloctaneCompound O:4-ethyl-2,3-dimethylhexane8

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesBasic IUPAC Nomenclature IVCycloalkanes Cycloalkanes have only carbon and hydrogen atoms. Formulas are CnH(2n) All the carbons in alkanes are sp3 hybridized and in a cycloalkane a ring isformed. (No ends) Cycloalkanes can be substituted like regular alkanesIUPAC Nomenclature of cycloalkanes follows these steps:1) Find the ring. This is now the main chain. Count the carbons and namechain as if it were a straight chain alkane. Add the prefix cyclo- to thename to get the full base name of the ring.2) If there are substituents:a. 1 substituent the carbon the substituent is attached to iscarbon-1. There is no need to number the substituent.b. 2 substituents the substituents will have the same numbers,so the first in alphabetical order will be at carbon-1. Substituentsshould be numbered.c. 3 or more substituents Number substituents so that thelowest possible numbers are used. If there is a tie usealphabetical order.3) Give each substituent a number according to which carbon itʼsattached to.4) List the substituents in alphabetical order in front of the main chain.a. Branched substituents get parenthesis around themb. Numbers are separated from numbers by commasc. Numbers are separated from words by hyphens5) Multiple straight chain substituents of the same kind are combined andgiven a prefix to indicate the number (di-, tri-, tetra-). These prefixes donot count towards alphabetical order. If the substituent is branched(bis-, tris-, tetrakis-) are used.6) Indicate stereochemistry using cis- or trans- prefixes for disubstitutedrings or R,S labels for multiply substituted rings.Notes: Cycloalkanes can become cycloalkyl substituents Two substituents on the same carbon are almost always 1,1-disubstituted. Cis-substituents are on the same side and sound similar, transsubstituents are on opposite sides and you have to go across the ring.9

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesExamples:ClClCompound CCompound DCl1)a cyclohexaneCla cyclopentaneCl2)Cl11252343butyl comes before propyland 1,3 is lower than 1, 51, 1, 3, 4 is lower than 1, 2, 4, 4(1,1 always wins)ethyl comes before methyl so wego counterclockwiseCl3)Cl11252331-sec-butyl or -4-methylcyclopentane(R)6)ClCl(R)(S)same side cis(S)(S)ethyl #1 CH, #2 CH2CCl2, #3 CH2CH3, #4 H Smethyl #1 CH, #2 CH2CCl2, #3 CH3, #4 H o-3-ethyl-4-methylcyclopentane10

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesPractice Cycloalkane Nomenclature:CH3BrClClCompound ACompound BCompound CCompound ECompound FBrClClCompound DClClClFCompound GCompound HBrClCompound JCompound IBrFCompound KCompound LCompound NCompound OBrBrCompound M11

Lievens,University of California, DavisJanuary 2012Chemistry 118 SeriesPractice Cycloalkane Nomenclature Key:Compound ound B:trans-1-chloro-2-isopropylcyclobutane ortrans-1-chloro-2-(1-methylethyl)cyclobutane pound C:1-butyl-2-sec-butyl-4-tert-butylcyclooctane cyclooctaneCompound D:2-bromo-1,1-dichlorocyclopropaneCompound E:1,3-diethyl-5-isopropylcycloheptane d F:cis-1-ethyl-3-isobutylcyclopentane orcis-1-ethyl-3-(2-methypropyl)cyclopentane pound G:trans-1-ethyl-3-isopropylcyclopentane ortrans-1-ethyl-3-(1-methyethyl)cyclopentane ound H:1-sec-butyl-2-chloro-4-ethyl-3-methylcyclohexane ohexaneCompound nd J:2-chloro-5-cyclobutyl-4-ethylheptaneCompound K:cis-1-bromo-4-tert-butylcyclohexane ound pound M:1,2-dibromo-3-ethyl-5-isopropylcyclohexane Compound N:trans-1-cyclopropyl-3-propylcyclohexane d yl)-4-propylcyclooctane12

sec-butyl H CCC H H H H H the sec- prefix is italicized and separate from the name and is NOT included in . January 2012 University of California, Davis Chemistry 118 Series 4 Branched alkyl groups can also be named by IUPAC by treating each branch as a substituent off the main cha

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