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Reference Guide

Organic Chemistry Nomenclature - Reference Guides

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University of Chicago
CHEM 22700

permacharts TM O r g a n icC h e m is t ryN o m e n c la t u r e Naming Organic Compounds •There are over 10 million known or• Names of organic compounds consist of three parts: Substituents + Parent Chain Prefix + Functional Group compounds; thousands are synthesized weekly Namethefollowingcompound: Parent name: Name of the alkane corresponding to the longest continuous chain of  The parent chain of an organic c Branches (or branch points) are Functionalgroupsareatoms(orgroup Isomers are compounds that have the same 44 33 22 11 Substitutive nomenclature: Treats an is the longest continuous carbon caoms to which substituents are atofatoms)andtheirassociatedbondsthamolecular formula but different str3ctu2es 2CHCH 3 organic compound as a substituted alkanee highest ranked functional group • If two definethestructureandchemicalproperties (.g.,1-bromobutane,2-nitropentane) different carbon chains with the highest(numericallocations)arenumbofaparticularfamilyofcompounds(e.g.,stitutional (formerly structural) isomCHs3 OH Genericname:Namenotdirectlyderivedfrompriority group and same number of isbonded•Allcarbonatomsintheparentalogens,carbon-carbondoubleandtri(i.e.,bonds must be broken in order to make systematicnomenclature;inventedonrequestoms are possible,then the one wicainarenumberedinthedirectionthatgives,–OH,–2H ,carbonylgroup(>C=O)to isomers equivalent) 4-methyl-2-hexanol (orafee)byU.S.AdoptedNamesCouncil most branches is the parent chain thelowestnumber(1)tothehighestpriorityxylgroup(–COOH)•Compounds Trade name: Name by which different Substituents are atoms or groups ofgroup,(2)tothesubstituentatfirstpointofningthesamefunctionalgroupundergoisomers are compounds with theof substituesuffix: The suffix companies call a given product; trade that replace hydrogen atoms on parbranching,and(3)atfirstpointofdifferencereactionscharacteristicofthatgroupnnectivity of all atoms but attached to -e in the parent are different from generic names i spatial arrangements of those atothe parent chain (i.e., hexane) Systematicname: Namederivedby SIMPLIFIED RULES FOR NAMING ORGANIC COMPOUNDS chain is replaced by followingaset of rulesdevelopedbyIUPAC identifying an (heInternational Unionof PureandAppliedcate highest ranked functional Number the carbon atoms in the parsubstituents are attached to the same carbon  Writenameof compounposition of methylohol Chemistry) •IUPACruleshavebeenupdatedmanyunctional group is normally idechain • If the branch point is thatom,then give them the same numbe•Namesandnumbersof substituentsagroup on parent timessincethefirst conferenceinGeneva(1892)suffix added directly to end nmber of carbon atoms from each eor more identical substituents in pefixes,parent chainisthestemof chainme, Locant: Identifies •Thegoal of theIUPACrulesistoarriveat aone- prefix then begin numbering at the end nare indicated by the use of the nuandfunctional groupisthesuffix•Hyphens group on parent chainl word,unambiguousnamefor eachcompound Determine parent chain • Parent chain isecond branch point hepta-,octa-, nona-,deca-,etc.-,heareusedtoseparatenumbers•Substituentsmas •Notwocompoundscanhavesamename,but longest continuous carbon chainthIdentify the substituents • Name each arearrangedalphabetically Note: Numbering begins from the it ispossibletohavemultipleIUPACnamesfor aest ranked functional group ansubstituent and precede this name with thetereochemistry of the molecule right side; therefore, the –OH group particular compound(especiallyfor complicateds • Parent chain name is a number of the carbon atom on the parentcis-,trans-,(R),(S),(E),(Z) wherecal prefixes(di-,tri-,etc.) arenot takenprecedence in the structures) determined by number of carbons inchain to which it is bonded • If two (or more)with their locants,if necessary) whenalphabetizingsubstituents gets the lower number Aliphatic Hydrocarbons Carbon Compounds Isomerism • Organic chemistry is the study of compounds containing carbon ALKANES CIS-TRANS OR E/Z ISOMERS • Hydrocarbons with only single bonds • Names of alkanes have suffix -ane(except CO,2CO , carbonates) • Carbon-carbon double bond consists of a s bond and a p bond Special characteristics: Carbon is tetravalent (forms four bonds with other Acyclic Alkanes, Cn 2n+2(n = 1, 2, 3, etc.) carbon atoms and/or other atoms like H, N, O, P, S, halides) • Carbon can formevents free rotation about the C=C,so stereoisomers are possible Nomenclature: Select longest continuous carbon chamethane 1 stable double and triple bonds with other atoms to form all kinds of chain-tituted alkenes and cycloalkanes may exist as cis-trans isomers; the parent name; characterized by suffix -ane • Numberethanens 2 lke and ring-shaped molecules, making the number of potential organicomer is designated cis if both substituents are on the same side of the carbon- carbon double bond or ring,and is designated trans if both substituents are on in chain from either end so that first substituentpropanewe3t compounds almost infinite (Note: Molecular formulas are not used in organic locant number • Basis for naming many organic compbutane 4 chemistry because even the simple formula can represent many structures)ite sides of the double bond or ring Branched Alkanes pentane 5 • Saturated compounds have only single bonds (may be acyclic or cyc• E-Z system of nomenclature describes the configuration about carbon- hexane 6 • Unsaturated compounds have at least one multiple (double or triplcarbon double bond (alkenes) • Each group on the two carbon atoms of the • Alkanes do not have a functional group so the naheptane 7 between two carbon atoms or a carbon and another type of atom (e.g.double bond is assigned a priority according to the Cahn-Ingold-Prelog rules branched alkane has the same stem and suffix -ane octane 8 >C C , C = N,>C O ) • Aromatic compounds are cyclic with 4n + 2 and the priorities are compared • The isomer in which the groups of higher that of a straight chain alkane nonane 9 delocalized p electrons • Heterocyclic compounds are cyclic compounds Nomenclature:  Determine the parent chain (longesdecane 10 with at least one atom in the ring other than carbon (usually O, N or S)ity on each carbon atom are on the same side of the double bond is continuous carbon chain; if more than one chain has the same designated (Z) • If the two groups of higher priority are on opposite sides, CH3CH2CH2CH3 O CH2 CH 3 methylcyclopropanethe isomer is (E) • The E-Z system is more universal and may be used for lngth,choose one with the most branches)  Number the carbon atoms butane CH2 CH2 CH2CH 2 CH (branched, cyclic)di-, tri-, and tetra-substituted alkenes • It cannot be used for cycloalkanes the parent chain • If branch point is the same number of carbon atoopen-chain), oxirane cyclopropaneCH2 CH2 •The cis-alkene can be also named (Z)-alkene; trans-alkene can be also each end,then begin numbering at the end nearer the second branch point (heterocyclic)(unbranched, cyclic) • If still the same,then go further down the chain till first point of difference named (E)-alkene (but not always vice versa) m • If numbering from either end gives the same numbers,begin numbering from • E/Z and cis-trans stereoisomerism is not possible when one of the the end giving lower number to the substituent that comes first in alphabet doubly bonded carbon atoms bears two identical substituents  Identify the substituents; name each substituent and precede this nameahn-Ingold-Prelog Rules o H3CCCC 2H3 HHCC 2CH3 H CC CH3 H3CCC CH 2H3 with its locant (if two or more substituents are bonded to the same carbon atom, rules designates the configuration of stereocenter (R oH S) Hr H3C H H CH 3 H CH3 c repeat the same locant for each substituent)  Use numerical prefixes (di-,tri-,ry of an alkene (E or Z) • Each substituent is assigned a . etc.) to indicate two or more identical substituents in a molecule Write they applying the following rules: or (Z)-2-penteneor (E)-2-penten(no stereoisomers-(no cis-transntene name as a single word with all substituents arranged alphabeticallyRule 1efixPriorities are first assigned on the basis of atomic number; possible) equivalent) s •When deciding the alphabetical order,ignore numerical prefixes (e.g.,di-,trithe higher the atomic number of the atom bonded directly or prefixes used in common names like sec- or tert- • Note:The names CHIRAL CENTER: R-S NOTATION t isopropyl and isobutyl are accepted by IUPAC and the prefix to the stereocenter, the higher its priority R S CH Rule 2 For isotopes, the one with highest atomic mass has • Chiral center, chiral carbon atom, asymmetric r iso- is included as a part of the word’s alphCH CH3ation highest priority carbon atom, stereocenter or, more recently, CH3 3 CH2CH3 stereogenic center describe a tetrahedral carbon a CH3CH2CC2 C3 3,6-diethyl-H3CH2 CHCH2CHC CH3 Rule 3 If priority cannot be assigned by applying Rules 1 and 2 because atom that bears four different substituents CH3 3,3-dimethylpenta2,5,6-trimethyloctaneH3C CH2CH3 two atoms of the same atomic number are bonded to the • Not all molecules which have a stereogenic mirror stereocenter, then compare atomic numbers of the second W W h ALKENES, Cn 2n atoms in each group; continue comparing atomic numbers center are chiral (e.g., meso compounds) • Unsaturated hydrocarbons that contain one or more C=C double bonds as necessary until a difference is found • The precise arrangement of substituents Xt CX Z Z C c Note: The double bond is considered a functional group a chiral center is its absolute configuration Rule 4 Multiple bonds are assigned single-bond equivalents Y Y a Nomenclature:  Ending -ane in parent alkane is changed to -ene • Select • Absolute configuration (R or S) is assigned If X is loweste longest continuous chain containing both carbon atoms of the double bond such that: (i) All substituents are ranked in ranked group  Number the chain from the end closer to the double bond (regardless of order of decreasing precedence according W W m positions of substituents)  Identify substituents  Identify stereochemistrys & Groups to the Cahn-Ingold-Prelog Rules; (ii) The C C (cis- or trans- for disubstituted alkenes; E or Z for di-, tri-, or tetra-substituted molecule is oriented so that the lowest- Y Z Z Y r alkenes)  Write the name as a single word: first stereochemistry indicator, F Ethyl CH2CH3 ranked substituent points away from you; Chloro Cl Propyl CH2CH2CH3 (iii) If the order of decreasing precedence R S e then substituents, then locant of double bond, then stem of parent Bromo, Br If priorities of W,Y, and, finally, suffix -ene CH2 CHCl chloroethene Isopropyl CH(CH3 2 of the three highest-ranked substituents apand Z are increasing in p CH2 CH2 CH3CH CH2 (C3 2 CHCH C2 (vinyl chloride) Iodo I Butyl CH2CH2CH2CH3 in a clockwise sense, then absolute configurationce (W
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