Does seeing a chemical name ever make you think, 'Wow, that’s complex? You're definitely not alone in feeling that way. To avoid misunderstandings and keep everything systematic, Chemists rely on a special system called IUPAC nomenclature. This system makes these names easy to understand worldwide. Imagine it as a global language for chemistry or a globally recognized system of rules designed to help scientists name the chemical names of compounds in an organized way and make them easy to understand worldwide. Instead of relying on the common names that can vary across regions and languages, IUPAC names adhere to a systematic and standardized pattern, enabling chemists to infer a compound’s structure and composition simply by analyzing its name. Throughout this lesson, we'll simplify the process step by step, helping you understand that naming organic compounds is easier than you might think.Under the IUPAC system, names of organic compounds are structured into three essential parts.(a) Word root (b) Prefix (c) Suffix l.toLowerCase().replace(/\s+/g,"-")" id="0fdcd894-d9cc-4ec2-818e-435f1905f080" data-toc-id="0fdcd894-d9cc-4ec2-818e-435f1905f080">(a) Stem Name or Word Root:In systematic nomenclature, the stem name or word root serves as the core unit, indicating the structure of the carbon chain. For the first four carbon structures, the stem names originate from the older trivial system, while the stem names for five or more carbon atoms follow Greek numerical conventions. The table below lists some of these; Table: Stem Names Used In IUPAC System For Carbon ChainNumber ofcarbonatomsNameNumber ofcarbon atomsNameNumber ofcarbon atomsName1Meth11Undec21Heneicos2Eth12Dodec30Triacont3Prop13Tridec40Tetracont4But14Tetradec50Pentacont5Pent15Pentadec51Henpentacont6Hex16Hexadec60Hexacont7Hept17Heptadec70Heptacont8Oct18Octadec80Octacont9Non19Nonadec90Nonacont10Dec20Eicos100Hectl.toLowerCase().replace(/\s+/g,"-")" id="054a6950-4ee3-4f32-929e-e449b6cc8ad6" data-toc-id="054a6950-4ee3-4f32-929e-e449b6cc8ad6">(b) Prefix:In nomenclature, stem name or word root may be modified by the attachment of certain groups or atoms, which are referred to as substituents. The names for these substituents are added as prefixes before the stem names. A selection of common substituents is provided in the tables below. Table: List Of Some Common Substituents Always Used As PrefixSubstituentsPrefixSubstituentsPrefix-FFluoro-NO2Nitro-CIChloro-ORAlkoxy-BrBromo-NONitrose-1Lodo-RAlkylThe following table also lists some common alkyl and related substituents.Alkyl Groups [R]Alkenyl and Alkynyl Groups [R]IUPAC name[Common acceptable formula]Condensed structuralformulaIUPAC name[Common andacceptable name]Condensed structural formulaMethyl (abbrev-Me) -CH₃Methylene CH₂=Ethyl (abbrev-Et) -CH₂CH₃Ethenyl [Vinyl]CH₂=CH-Propyl (abbrev--Pr)-CH₂CH₂CH₃ PropenylCH₂CH=CH- 1-Methylethyl[isopropyl]Prop-2-enyl[Allyl]-CH₂CH= CH₂Butyl [n-butyl]-CH₂CH₂CH₂CH₂CH₃ 1-Methylethenyl[isopropenyl]2-Methylpropyl [isobutyl] EthynylCH= C- 1-Methylpropyl·[sec-butyl]Aromatic Systems [Ar] 1,1-Dimethylethyl [tert-butyl] Phenyl(abbrev-Ph) C₆H₅−Pentyl[n-pentyl;amyl]-CH₂CH₂CH₂CH₂CH₂CH₃Benzyl(abbrev-Bz) C₆H₅CH₂− Tolyl C₆H₅CH₂−l.toLowerCase().replace(/\s+/g,"-")" id="569e3015-bac2-49bb-a5a6-6da958bb32d6" data-toc-id="569e3015-bac2-49bb-a5a6-6da958bb32d6">(c) Suffix:A suffix, signifying the functional group within a compound, is affixed to the stem name or word root, as referenced in the table. Table: Suffixes And Prefixes Of Some Common Classes Of Organic CompoundsS.NoClass of compounds(functional groups)FormulaSuffix[Column I]Suffix[Column II]Prefix1.Carboxylic acid-COOH-oic acidCarboxylic acidCarboxy2Sulphonic acid-SO3Hsulphonic acid-Sulpho3AnhydrideRCOOCOR'-oic anhydride- 4Esters-COO(R)(R)...oate(R)...carboxylateOxycatone5Acid halides-COX-oyl halideCarbonyl halideHalocarbonyl6Amides-CONH2AmideCarboxamideCarbamoyl7Nitriles-C=N-nitrileCarbonitrileCyano8Aldehydes-CHO-alCarbaldehydeOxo-, Fom9Ketones-one-Oxo-10Alcohols andPhenols-OH-o-Hydroxy-11ThiolsSH-thiol-Sulphany12Amines-NH2-amine-Amino-13IsocyanideIsonitrile-Isocyano14.Ethers-O(R)--(alk) oxy{alk is fo15.Alkenes-ene--16.Alkynes-yne--Functional groups in the table are given in decreasing order of preference(naming polyfunctional compounds. In naming, the highest-priority functional group is indicated by a suffix, and the remaining groups are prefixed. Suffixes in Column II represent the alternative suffix for a class of organic comp where the carbon of the principal functional group cannot be included in the longest cont carbon chain. l.toLowerCase().replace(/\s+/g,"-")" id="1796536e-1f09-4c4d-b93f-76dbb8114f76" data-toc-id="1796536e-1f09-4c4d-b93f-76dbb8114f76">Naming The Organic Chemistry structures According to the IUPAC naming system, specific rules govern the naming of different classes of organic compounds. Let us discuss these rules for various families.Naming The Alkanes: Outlined below are the various steps involved in naming alkanes according to IUPAC guidelines;1. Unbranched alkanes are named by adding a suffix to the word root. The carbon atoms in a compound are indicated by stem name. Here are a few illustrative examples of IUPAC names applied to unbranched alkanes.CH4MethaneCH3(CH2)7CH3NonaneCH3-CH3EthaneCH3(CH2)8CH3DecaneCH3CH2CH3PropaneCH3(CH2)9CH3UndecaneCH3(CH2)2CH3ButaneCH3(CH2)10CH3DodecaneCH3(CH2)3CH3PentaneCH3(CH2)11CH3EicosaneCH3(CH2)4CH3HexaneCH3(CH2)12CH3HeneicosaneCH3(CH2)6CH3HeptaneCH3(CH2)13CH3TriacontaneCH3(CH2)7CH3OctaneCH3(CH2)14CH3Hectane2. For branched chain alkanes, the longest possible continuous chain or parent chain of carbon atoms is selected. The compounds are called derivatives of alkanes, and the number of carbon atoms in a chain represents the number of alkanes.3. The chain is numbered from the end, which provides the lowest numerical designation for the carbon atom with the allyl substituent. For numbering, we use Arabic numerals 1, 2, 3,...., and so on.4. To indicate the alkyl group's position, the alkyl substituent is defined by the number given to the carbon atom to which it is bonded.5. In the name, the locant(number), specifying the position, comes before the alkyl group.6. Under this method, the compound name is written in a single-word format. A hyphen separates a word and a number, and a comma separates two numbers.7. Prefixes including n-, iso-, neo-, tert-, sec-, and others are not employed unless necessary. For example,3-Methylpentane2-Methylpentane4-ethylheptane8. The various alkyl groups in a compound are listed in alphabetical order., no matter where they are positioned along the carbon chain. The different alkyl groups present in a compound are written in alphabetical order, irrespective of their position in the carbon chain. Ethyl is written first due to alphabetical preference over methyl, regardless of the order of its position.3-Ethyl-2-methylpentaneNot 2-Methyl-3-cthylpentane 9. For compounds with multiple identical alkyl groups, prefixes such as di-, tri-, tetra-, and so on are employed to specify their count along the carbon chain. However, the multiplicative prefixes are used independently. For example,2,3-dimethyl pentane 10. If two distinct alkyl groups are positioned equally from either end of the chain, the alkyl group that precedes alphabetically gets the lowest numerical designation. For example,3-Ethyl-4-methyl hexaneNot 4-Ethyl-3-methyl hexane11. For compounds with over two alkyl groups where the branches are symmetrically placed, numbering starts from the end and yields the smallest set of locant values for all substituents. For example2,3,5-trimethylhexane12. All three methyl groups (locant) get the lowest possible numbering from this end. 13. When the substituent is a branched chain alkyl group, it is numbered separately, starting from the point it is attached to the parent chain. The branched alkyl group is always prefixed in brackets. 5-(1-methylpropyl) nonanel.toLowerCase().replace(/\s+/g,"-")" id="18b69ec4-7ab1-4929-ab87-3ff89ad133b7" data-toc-id="18b69ec4-7ab1-4929-ab87-3ff89ad133b7">Naming The Alkenes:The fundamental rules for naming alkenes are largely similar to those used for alkanes, but we additionally specify the location of the double bonds here.(1) Identify the longest continuous chain of carbon atoms, ensuring that the double bond's carbons are part of it.(2) Name the longest chain by substituting the 'and' suffix with 'ene.'(3) The carbon having a double bond always gets the lowest number.(4) The carbon has a double bond, which is preferred over the substituent attached to the parent chain.(5) For alkenes, the double bond's location is designated by placing its number prior to the suffix 'ene.'Examples:CH2=CH2 CH3-CH=CH2Ethene Propene CH3-CH2-CH=CH2 CH3-CH=CH-CH3But-2-en But-1-en3-ethyl-4-methylpent-1-ene 6. If multiple double bonds are present, the locations of each bond are specified by their respective numbers positioned just before the suffix. The naming convention employs the suffix 'diene' for molecules with two double bonds, 'triene' for those with three, and additional double bonds follow a similar pattern. The general name for dienes is 'Alkadiene'. 1 2 3 4 5 1 2 3 4 5H2C=CH-CH=CH-CH3 H2C=CH-CH-CH=CH2·Penta-1,3-diene Penta-1,4-dienel.toLowerCase().replace(/\s+/g,"-")" id="8d32eddb-47f3-415b-b886-8bec3983fe3b" data-toc-id="8d32eddb-47f3-415b-b886-8bec3983fe3b">Naming The Alkynes:(1) Select the longest possible chain, which includes the cabins of the triple bonds.(2) To name an alkyne, the '-ane' ending of the corresponding alkane is replaced with '-yne’.(3) The first carbon of the triple bond gets the most extended number. All subsequent rules are consistent with the rules for alkanes. Consider these few examples of alkynes. (4) A compound having two triple bonds is named Alkadiyne. A number is put before the –dyne that indicates its position.Penta-1,4-diyne Penta-1,3-diynel.toLowerCase().replace(/\s+/g,"-")" id="385c6c35-e7c4-40e6-ad00-a29e75f69ff3" data-toc-id="385c6c35-e7c4-40e6-ad00-a29e75f69ff3">Naming The Cyclic Aliphatic Hydrocarbons:(1) We use the prefix cyclo- to alkane in this case.(2) If an alkyl group is attached to a cyclic structure as a substituent, it is termed alkyl cycloalkane.(3) For cyclic compounds containing multiple alkyl substituents, the positions and names of these groups are assigned to follow the same rules that are applicable to alkane.(4) If the cyclic structure is unsaturated, the carbon atoms bearing the double bond get priority (C>) over the other substituents present in the cyclic structure.l.toLowerCase().replace(/\s+/g,"-")" id="d4848aeb-4178-406d-97e2-07a8ca9cf5ac" data-toc-id="d4848aeb-4178-406d-97e2-07a8ca9cf5ac">Rules For Nomenclature Of Cycloalkanes:(1) The numbering of the carbon atoms in the ring is done so that the substituent that comes first in the alphabetical order is given the lowest possible number, provided it does not violate the lowest set of locants rule.(2) When the ring contains more or an equal number of carbon atoms than the alkyl group attached to it, then it is named a derivative of cycloalkane, and the alkyl group is treated as a substituent.(3) Suppose the alkane chain contains a more significant number of carbon atoms than is present in the ring. In that case, the compound is considered a derivative of alkane, and the ring is designated as a substituent.(4) Alphabetical order for the substituents (Ethyl over methyl) is taken into consideration for naming.Cycloalkenes And Cycloalkynes:(1) The word cyclo is prefixed before the names of alkenes and alkynes, and it has the same number of carbon atoms as the ring.Cyclobutene Cyclopentene Cyclohexene (2) In the case of substituted cycloalkenes and cycloalkynes, the numbering of double or triple bonds is 1 and 2. The direction is chosen to give the lowest numbers to the substituents.3-Methylcyclohexene 3-Methylcyclobutynel.toLowerCase().replace(/\s+/g,"-")" id="49f50467-2b76-406b-abda-a86ff919405d" data-toc-id="49f50467-2b76-406b-abda-a86ff919405d">Alicyclic Compounds Containing Functional Groups:(1) Alicyclic alcohols, aldehydes, ketones, acids, etc., are named in the same fashion as corresponding aliphatic compounds by prefixing the word 'cyclo' before the name.l.toLowerCase().replace(/\s+/g,"-")" id="caece931-4be3-40fd-b458-23e069e5d0e3" data-toc-id="caece931-4be3-40fd-b458-23e069e5d0e3">Naming The Alkyl Halides (RX)(1) When alkyl halides are named, the halogens are always treated as substituents. They are written as prefixes to the name of a compound.(2) The alkyl halides are named as Haloalkane. (3) The carbon with halogen is given the lowest possible numbering during the selection of the longest chain.l.toLowerCase().replace(/\s+/g,"-")" id="445c3677-248e-470f-a641-5dc114ffd9b1" data-toc-id="445c3677-248e-470f-a641-5dc114ffd9b1">Naming The Alcohols(1) Select the longest continuous chain of carbon atoms containing the hydroxy group.(2) The suffixing -ol for the -e of the corresponding alkane is added. Thus, alcohols are named as Alkanols.(3) The carbon having the hydroxyl group is given the lowest possible number. For example(4) Those alcohols which contain two or more hydroxyl groups are commonly known as polyhydric alcohols. In the IUPAC system, suffixes -diol, -triol, and so on are used for them. In such cases, the vowel 'e' of alkane is retained in the name. Thus, the alkane bearing two hydroxyl groups is named Alkanediol.(5) The unsaturated alcohols are named by replacing -ane by suffix-enol (ene + ol) or-ynol (yne+ol) of the corresponding alkanes.l.toLowerCase().replace(/\s+/g,"-")" id="8b283c43-5b20-41a9-a762-50dc9bb8553a" data-toc-id="8b283c43-5b20-41a9-a762-50dc9bb8553a">Naming The Ethers (ROR')(1) In the IUPAC system, the name for ethers is akoxyalkane.(2) Select the longest continuous carbon chain and give the name as alkane. The chain with a lesser number of carbon atoms is named alkoxy and is always written as substituent with the number specifying its position. For example, CH3-O-CH3 CH3-O-CH2-CH3Methoxymethane MethoxyethaneNot Ethoxymethane(3) There are two ways to name the cyclic cu.(i) Epoxy is commonly used as a prefix for 3-membered cyclic ethers.(ii) Considering it as a heterocyclic compound, this is commonly used for high-membered cyclic ethers.l.toLowerCase().replace(/\s+/g,"-")" id="aa2d4f28-e58c-4a3b-a8d0-b5f5a4bceeea" data-toc-id="aa2d4f28-e58c-4a3b-a8d0-b5f5a4bceeea">Naming The Aldehydes (RCHO):(1) Select the longest continuous carbon chain-containing group, and the carbon-CHO group gets the lowest number.(2) Add the suffix-al in place of -e of the corresponding alkane. Thus, in general, an aldehyde is named Alkanal.(3) The numbering starts from the aldehydic carbon, but the position of the aldehyde is specified by the number '1', as it is understood that aldehydic carbon is the term carbon.(4) Those compounds that have two aldehydic groups are named alkanedial, and so where vowel 'e' of alkane is retained.(5) The unsaturated aldehydes are named alkenal (ene + al) and alkynal (yne+al).HCHO Methanal(Formaldehyde) CH3CHO Ethanal (Acetaldehyde) CH3CH2CHOPropanal OHC-CHOEthanedial 4 3 2 1 CH3CH=CH-CHO But-2-enal l.toLowerCase().replace(/\s+/g,"-")" id="4b7ea854-4cb7-4025-a6a9-60f9a23af7e9" data-toc-id="4b7ea854-4cb7-4025-a6a9-60f9a23af7e9">Naming The Ketones (RCOR'):(1) Select the longest continuous carbon chain, and it must contain a ketonic group.(2) The suffix -one is added in place of -e of the corresponding alkane. Thus, the name Alkanone.(3) The carbon chain is numbered so that the ketonic group gets the lowest number.(4) The substituents' positions are numbered, and they are placed as prefixes according to the rules explained earlier.(5) Those compounds that contain two ketonic groups are termed Alkanediones, along with the number of groups in position. So, the vowel 'e' of the alkane is written in this scenario.(6) The unsaturated ketones are called Alkenones (ene + one) or Alkynones (yne + one).l.toLowerCase().replace(/\s+/g,"-")" id="9100bf5e-2ebd-4e79-a584-6cd1d8e21670" data-toc-id="9100bf5e-2ebd-4e79-a584-6cd1d8e21670">Naming The Carboxylic Acids (RCOOH):(1) Select the longest continuous carbon chain that must contain the carboxylic group and get the lowest number.(2) The suffix -oic acid is added in lieu of -e of the corresponding alkane. Thus, the Alkanoic acid.(3) The name of a carboxylic acid is written as two words.(4) The general names of the family of unsaturated carboxylic acids are alkenoic acid and alkynoic acid.(5) For dicarboxylic acids, the longest chain should include both carboxylic groups, starting from one carboxylic group and terminating at the other. Thus,nam dicarboxylic acids are Alkanedioic acid. It is written without specifying the position of the carboxylic acids.HCOOHMethanoic acid(Formic acid) CH3COOHEthanoic acid(Acetic acid)CH3CH2COOHPropanoic acidl.toLowerCase().replace(/\s+/g,"-")" id="f219f307-818e-4482-939c-8f3dee7409fc" data-toc-id="f219f307-818e-4482-939c-8f3dee7409fc">Naming The Alkyl Cyanides (RCN) Isocyanides And Nitroalkanes:(1) Alkyl cyanide is named as alkane nitrile.(2) The selected longest chain must include the carbon of the cyanide group (-CN), which gives the lowest number.HCN CH3-CNMethanenitrile Ethanenitrile(Hydrogen cyanide) (Acetonitrile)l.toLowerCase().replace(/\s+/g,"-")" id="f0115aea-d397-4feb-8796-7109b0344249" data-toc-id="f0115aea-d397-4feb-8796-7109b0344249">Naming The Alkyl Isocyanides (RNC):Isocyanides are named as Alkaneisonitriles. Earlier, they were referred to as carbylamine derivatives. When selecting the parent chain, the carbon of isonitrile is omitted, for example.l.toLowerCase().replace(/\s+/g,"-")" id="4b3e861c-01b9-4b4c-b243-3d886b4f6571" data-toc-id="4b3e861c-01b9-4b4c-b243-3d886b4f6571">Naming The Nitroalkanes (RNO2)The nitro group is always treated as a substituent and written as a prefix along with its position on the longest continuous carbon chain. For examplel.toLowerCase().replace(/\s+/g,"-")" id="8f847c2d-613f-4a22-8d81-0e86f7c9676b" data-toc-id="8f847c2d-613f-4a22-8d81-0e86f7c9676b">Naming The Amines (RNH2):(1) Select the most extended continuous carbon, which includes the carbon attached to the -NH2 group.(2) The suffix -amine is added in place of -e of the corresponding alkane. Thus, the general IUPAC name for amines is Alkanamine.(3) During the numbering of the parent chain, the lowest possible number is given to the carbon attached to the –NH2 group. For example(4) For secondary amines, the longer chain is selected as a parent chain. The other alkyl group is named as a prefix and written as N-alkyl before the parent chain. Thus, they are named N-alkylalkanamines.(5) The longest chain is selected for tertiary amines as a parent chain, and the other two alkyl groups are written as prefixes. N, N-dialkyl if both alkyl groups are the same, and N-alkyl-N-alkyl if both are different.l.toLowerCase().replace(/\s+/g,"-")" id="a1817f63-685a-496b-8f02-6d7b5ca29679" data-toc-id="a1817f63-685a-496b-8f02-6d7b5ca29679">Naming The Thioalcohols (R-SH):(1) The IUPAC name for thioalcohol is Alkanethiol.(2) The lowest possible number is given to the carbon bearing the-SH group.l.toLowerCase().replace(/\s+/g,"-")" id="fdb45c82-84c6-42bd-a709-160ba0882f75" data-toc-id="fdb45c82-84c6-42bd-a709-160ba0882f75">Naming The Sulfonic Acids (RSO3H):(1) Select the longest continuous carbon chain, which includes the carbon having a SO3H group.(2) The general IUPAC name is Alkanesulphonic acid.(3) The carbon having-SO3H group gets the lowest possible order of numberingl.toLowerCase().replace(/\s+/g,"-")" id="74d45d89-1682-4fdf-a883-efbcf93aa23a" data-toc-id="74d45d89-1682-4fdf-a883-efbcf93aa23a">Writing The Structure Of An Organic Compound From Its IUPAC Name:The following steps are to be followed to write the structure of an organic compound using its name. For example, consider 5-chloro-6-methylheptan-2-ol.(1) The carbon skeleton is written as indicated by the parent chain name. In this case, it is kept as a seven-carbon skeleton. Now, count and number the carbon skeleton from one end.(2) Identify the principal functional group and place as indicated by the name. In this case, the principal functional group is alcohol (-OH), present at the second carbon.(3) The rest of the substituents are placed at the indicated positions.(4) Now, hydrogen (s) are placed to satisfy the valency of the carbon skeleton. Thus, the structure of an organic compound can be written as follows: