Chp. 3 Nomenclature Chemistry PDF

IUPAC naming IUPAC (the International Union of Pure and Applied Chemistry) is the organization responsible for our current organic chemistry naming system. In general, all organic compounds’ IUPAC names look like this: Substituents + parent chain So, what is a substituent? Quite simply, a substituen...

IUPAC naming IUPAC (the International Union of Pure and Applied Chemistry) is the organization responsible for our current organic chemistry naming system. In general, all organic compounds’ IUPAC names look like this: Substituents + parent chain So, what is a substituent? Quite simply, a substituent is any appendage dangling off of the molecule’s parent chain. And what is a parent chain? What is a Parent Chain? Generally speaking, an organic molecule’s parent chain is the longest chain of atoms (mostly carbon atoms) that contains the molecule’s highest-priority functional group. What is a functional group? Well, in the world of organic chemistry, every molecule contains different parts of it that can participate in chemical reactions. These reacting parts are called functional groups. Highest priority Functional group (general formula) R = any CXHY chain Carboxylic acid (RCO2H) Ester (RCO2R') Acid chloride (RCOCl) Amide [R'C(O)NR2] Nitrile (R–C≡N) Ethanoic acid, propanoic acid, butanoic acid, etc. Ethyl ethanoate, methyl propanoate, etc. Ethanoyl chloride, propanoyl chloride N,N-dimethyl propanamide; N-ethylbutanamide Ethanenitrile, propanenitrile, etc. Alkoxycarbonyl Chloroformyl Amido Cyano Aldehyde ( ) Ethanal, propanal, butanal, etc. Oxo or formyl Ketone ( ) 2-butanone, 3-butanone, 2-pentanone Oxo Methanol, ethanol, propanol, etc. Hydroxy N,N-dimethylpropanamine, Nethylcyclohexanamine Amino Alcohol (ROH) Phenol (PhOH) Lowest priority Examples (if parent): If it’s a substituent to a higher-priority group, then it’s called: Amine (R'-NR2) Alkene ( Alkyne ( Ether (R'OR) Alkyl halide (RX) X = F, Cl, Br, or I Nitro (NO2) ) Ethene, propene, butene, etc. ) Ethyne, propyne, butyne, etc. Methoxyethane, ethoxypropane 2-bromopropane, 3-chlorobutane, etc. N/A methoxy, ethoxy, propoxy, etc. Fluoro, chloro, bromo, iodo, etc. Nitro IUPAC naming You need to memorize the following IUPAC names for simple hydrocarbon parent chains: Number of Carbons Parent Alkane Name Molecular Formula (CnH2n+2) Condensed Structure 1 Methane CH4 CH4 2 Ethane C2H6 CH3CH3 3 Propane C3H8 CH3CH2CH3 4 Butane C4H10 CH3CH2CH2CH3 5 Pentane C5H12 CH3CH2CH2CH2CH3 6 Hexane C6H14 CH3CH2CH2CH2CH2CH3 7 Heptane C7H16 CH3CH2CH2CH2CH2CH2CH3 8 Octane C8H18 CH3CH2CH2CH2CH2CH2CH2CH3 9 Nonane C9H20 CH3CH2CH2CH2CH2CH2CH2CH2CH3 10 Decane C10H22 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 IUPAC naming You should also memorize these simple substituent names and structures: For alphabetical purposes, isopropyl and isobutyl start with an “I” because they don’t have a hyphen. However, tert-butyl and sec-butyl are alphabetized based on “B” because it is hyphenated. IUPAC naming You should also memorize these simple substituent names and structures: Naming Alkanes Alkanes are organic compounds that only have H’s and C’s in them, with no double or triple bonds in them. Ringed alkanes are called cycloalkanes. Here are the steps of naming alkanes: 1. Find the parent chain: In general, the parent chain is the longest carbon chain. If two possible parent chains have the same length, but different substituent numberings, pick the one with the smaller substituent number at the first point of difference. 2. Count the number of carbon atoms in the parent chain and match that number to the name from our earlier chart (methane, ethane, propane, etc.) Naming Alkanes Alkanes are organic compounds that only have H’s and C’s in them, with no double or triple bonds in them. Ringed alkanes are called cycloalkanes. Here are the steps of naming alkanes: 3. Identify and number the substituents (appendages dangling off the parent chain) in whichever direction gives them the lowest number. 4. Write the name as a single word: Substituents (replace “ane” with “yl”) + parent chain List substituents in alphabetical order, using the prefixes di-, tri-, etc. if the same substituent is present multiple times along the parent chain. Naming Alkanes Alkanes are organic compounds that only have H’s and C’s in them, with no double or triple bonds in them. Ringed alkanes are called cycloalkanes. Here are the steps of naming alkanes: 1. Find the parent chain: In general, the parent chain is the longest carbon chain. If two possible parent chains have the same length, but different substituent numberings, pick the one with the smaller substituent number at the first point of difference. 2. Count the number of carbon atoms in the parent chain match that number to the name from our earlier chart (methane, ethane, propane, etc.) First Point of Difference Question Provide an acceptable name for the alkane shown. 6 1 2 3 4 7 5 Substituents + parent chain Because our alkane chain is seven carbons long, its parent name is heptane. First Point of Difference Question we number Provide anShould acceptable name for the alkanegoing shown. left-to-right or right-to-left? 6 7 Because our alkane chain is seven We can answer this question by doing it its carbons long, parent name is 5 4 1 2 3 both ways and then seeing which way heptane. gives us the lower number AT THE FIRST POINT OF DIFFERENCE. Substituents + parent chain First Point of Difference Question Provide an acceptable name for the alkane shown. 6 7 5 1 2 3 4 Substituents + parent chain 5-ethyl-4,4-dimethyl heptane Because our alkane chain is seven carbons long, its parent name is heptane. First Point of Difference Question Provide an acceptable name for the alkane shown. 2 1 3 7 6 5 4 Substituents + parent chain 3-ethyl-4,4-dimethyl heptane Because our alkane chain is seven carbons long, its parent name is heptane. First Point of Difference Left-to-right Right-to-left 5-ethyl-4,4-dimethyl heptane 4,4,5 3-ethyl-4,4-dimethyl heptane 3,4,4 Once the numerical tie is broken, it doesn’t matter what happens after that. First Point of Difference Left-to-right 5-ethyl-4,4-dimethyl heptane Right-to-left 3-ethyl-4,4-dimethyl heptane Once the numerical tie is broken, it doesn’t matter what happens after that. Naming Cycloalkanes The rules for naming cycloalkanes are similar to those for naming regular alkanes. The differences are: For cycloalkanes, we put the prefix “cyclo” before the alkane, to indicate it’s a ringed compound. For cycloalkanes with two substituents, we use the prefix “cis” to indicate that those substituents are both pointing in the same direction. If those substituents are pointing in opposite directions, we use the prefix “trans.” trans-1-isopropyl-4-methylcyclohexane Naming Cycloalkanes The rules for naming cycloalkanes are similar to those for naming regular alkanes. The differences are: For cycloalkanes with more than two substituents, we can’t use the prefixes “cis” or “trans.” Instead, we have to use the R/S system. Naming Cycloalkanes The rules for naming cycloalkanes are similar to those for naming regular alkanes. The differences are: Just so you know, you CAN use the R/S system for any cycloalkane, including those for which the cis/trans convention is applicable. Naming Cycloalkanes If you have a non-cyclic alkane with a cyclic substituent attached to it, what do you do? The cyclic portion of the molecule is the parent chain, unless the non-cyclic portion is longer. In that case, the non-cyclic portion becomes the parent chain. sec-butylcyclohexane 4-cyclopentylheptane Naming Alkyl Halides When naming alkyl halides (carbon molecules that have halogens –F, Cl, Br, or I– in them), we follow the rules for naming alkanes, except that we: Use the prefixes “fluoro”, “chloro”, “bromo”, or “iodo”, with numbers, to identify each halogen substituent and its position. Alternatively, you can use the suffixes “yl fluoride”, “yl chloride”, “yl bromide”, or “yl iodide” at the end of the parent name for simple alkyl halides. Naming Alkenes When naming alkenes, we follow the rules for naming alkanes, except that we: Use “ene” instead of “ane” at the end of the molecule’s name. Add a number at the beginning of, or within, the name to indicate where the C=C bond starts. Naming Alkenes When naming alkenes, we follow the rules for naming alkanes, except that we: Use “ene” instead of “ane” at the end of the molecule’s name. Add a number at the beginning of, or within, the name to indicate where the C=C bond starts. Add the prefixes cis or trans, or alternatively, E or Z, at the beginning of the name to indicate the C=C bond’s stereochemistry. Cis and Trans Alkenes What’s the difference between these two molecules? trans-2-butene cis-2-butene Don’t Confuse Cis/Trans Alkenes with Cis/Trans Cyclics You should remember from a prior video that for rings with two substituents: if the two substituents are going in the same direction –either both up or both down– then they are cis to each other. If they’re going in opposite directions, then they’re trans to each other: trans-1,3-dimethylcycloheptane Don’t Confuse Cis/Trans Alkenes with Cis/Trans Cyclics With alkenes, if you have two substituents on opposite sides of the C=C bond, and they are pointing in opposing directions, then they are trans to each other. If they point in the same direction, then they are cis: E/Z Naming of Alkenes How do you think we would name these? Would they be cis or trans? Answer Using Cis or Trans to name alkenes only works if you have one hydrogen on each of the two alkene C=C carbons. If you don’t, then you have to use something called the E/Z naming system. Officially, you can ALWAYS use E/Z naming with all alkenes, but you can only use cis/trans on alkenes that have one H on each of the alkene C=C carbons. E/Z Naming of Alkenes If the two highest-priority groups are on “Zee Zame Zide” (the same side), then it is a Z alkene. If the two highest-priority groups are on “Epposite sides” (opposite sides), then it is an E alkene. How to Determine Priority To determine a substituent’s priority: 1. Highest atomic number = highest priority 1. If there’s a tie, then keep going out one atom at a time until you break the tie. 1. Multiple-bonded atoms are counted as the same number of single-bonded atoms: This C counts as being bonded to two O’s...... So it would outrank a carbon that was only singly-bonded to one O. Naming Alkynes When naming alkynes, we follow the rules for naming alkanes, except that we: Use “yne” instead of “ane” at the end of the molecule’s name. Add a number at the beginning of, or within, the name to indicate where the CΞC bond starts. or 3-heptyne Naming Alkynes When naming alkynes, we follow the rules for naming alkanes, except that we: Use “yne” instead of “ane” at the end of the molecule’s name. Add a number at the beginning of, or within, the name to indicate where the C=C bond starts. Naming Other Functional Groups Now that we have the basics down, I’m going to teach you how to IUPAC-name your way through a bunch of other functional groups. Highest priority Functional group (general formula) R = any CXHY chain Carboxylic acid (RCO2H) Ester (RCO2R') Acid chloride (RCOCl) Amide [R'C(O)NR2] Nitrile (R–C≡N) Ethanoic acid, propanoic acid, butanoic acid, etc. Ethyl ethanoate, methyl propanoate, etc. Ethanoyl chloride, propanoyl chloride N,N-dimethyl propanamide; N-ethylbutanamide Ethanenitrile, propanenitrile, etc. Aldehyde ( ) Ethanal, propanal, butanal, etc. Ketone ( ) 2-butanone, 3-butanone, 2-pentanone Alcohol (ROH) Phenol (PhOH) Lowest priority Examples (if parent): Methanol, ethanol, propanol, etc. N,N-dimethylpropanamine, Nethylcyclohexanamine Amine (R'-NR2) Alkene ( Alkyne ( Ether (R'OR) Alkyl halide (RX) X = F, Cl, Br, or I Nitro (NO2) ) Ethene, propene, butene, etc. ) Ethyne, propyne, butyne, etc. Methoxyethane, ethoxypropane 2-bromopropane, 3-chlorobutane, etc. N/A Naming Other Functional Groups Now that we have the basics down, I’m going to teach you how to IUPAC-name your way through a bunch of other functional groups: Alcohols, ethers, and amines What Are Alcohols, Ethers, and Amines? Functional group Description Alcohols Look like alkanes, except they have an OH in them Ethers Two alkanes joined by an O in the middle Amines Look like alkanes, except they have an N somewhere in them Examples Naming Alcohols When naming alcohols, we follow the rules for naming alkanes, except: Our parent chain is the longest carbon chain that has the OH (“hydroxyl”) group on it, EVEN IF THERE ARE LONGER carbon chains that don’t have the OH on them. Number the carbon chain in the direction that gives the smallest number to the carbon bonded to the hydroxyl (OH) group. Hydroxyl (OH) groups are higher-priority than cycloalkanes, amines, alkenes, ethers, and alkyl halides, so we must number in the direction that gives the OH the lowest possible number, even if it gives a higher number to any of these lower-priority functional groups. Naming Ethers 1. Name the two alkyl groups as substituents with the word “ether” at the end: or: 2. Consider the longest carbon chain to be the parent chain and the alkoxy group to be a substituent: 1 2 3 1 propane methoxy ethoxy propane 2 3 Naming Amines Amines can be 1°(primary), 2°(secondary), or 3°(tertiary), depending on how many carbons are bonded to the nitrogen: When four carbons are bonded to the nitrogen, the nitrogen gets a formal positive charge. The resulting compound is called a “quaternary ammonium salt”: Naming Amines Primary amines, RNH2 (R = any carbon chain), are named by adding the suffix “amine” to the name of the organic substituent: Symmetrical and secondary amines are named by adding di- or tri- to the alkyl group: Naming Amines Asymmetrical amines are named as N-substituted primary amines, with the largest alkyl group being named as a parent chain: ethyl and methyl 1 2 3 cyclohexylamine methyls propylamine Aldehydes and Ketones Naming Aldehydes When naming aldehydes, we follow the rules for naming alkanes, except: The parent chain is the longest carbon chain that contains the aldehyde. We number the parent chain in the direction that gives the smallest number to the aldehyde carbon. We replace the “e” in our alkane name with the suffix “al”. 5 4 3 2 butanal 4 3 2 1 1 1 4-methylpentanal methanal (formaldehyde) cyclohexanecarbaldehyde Naming Ketones There are two ways to name ketones: Name each chain on either side of the C=O (carbonyl) and then follow it with the word “ketone”. (Note: this isn’t really the IUPAC way, but you may see it.) 2 3 2 1 1 phenyl methyl ethyl propyl ketone methyl phenyl ketone Naming Ketones There are two ways to name ketones: (The actually IUPAC way): Name the entire parent chain as you would with an alkane, but replace the “e” in the alkane name with a number to indicate the position of the C=O (carbonyl) bond, followed by the suffix “one”. Be sure to number in whichever direction gives the C=O the lowest number. 5 1 6 6 4 3-hexanone or hexan-3-one 4 2 3 2 1 3 5 3,5-dimethyl-2-hexanone or 3,5-dimethylhexan-2-one Naming Ketones Please note that in cyclic ketones, the position of the C=O (carbonyl) is assumed to be #1 in the ring: Carboxylic Acid Derivatives Naming Carboxylic Acids When naming carboxylic acids, we follow the rules for naming alkanes, except: The parent chain is the longest carbon chain that contains the carboxylic acid. We number the parent chain in the direction that gives the smallest number to the carboxylic acid. We replace the suffix “e” in our alkane name with the suffix “oic acid”. 4 3 2 5 1 4 3 2 1 1 Naming Acid Halides When naming acids halides, we follow the rules for naming alkanes, except: The parent chain is the longest carbon chain that contains the acid halide. We number the parent chain in the direction that gives the smallest number to the acid halide. We replace the suffix “e” in our alkane name with the suffix “oyl halide”. 5 4 3 2 1 4 3 2 1 2 1 Naming Esters When naming esters, we follow the same pattern as we do for carboxylic acids and acid halides, except: In the name, the alkyl group attached to the ester oxygen gets listed first, as a substituent, with the suffix “yl”. The parent chain name then follows. The parent chain starts at the C=O (carbonyl) carbon and is counted moving away from the ester oxygen. In the name, the parent chain’s suffix “e” is replaced with “oate”. methyl 4 3 2 1 methyl butanoate butanoate Naming Esters alkyl group attached to the ester oxygen 4 5 2 3 1 ethyl pentanoate pentanoate alkyl group attached to the ester oxygen 6 5 4 3 2 1 cyclopentyl hexanoate hexanoate Naming Esters (methyl butanoate) (methyl propanoate) methyl ethanoate (methyl acetate) Naming Amides When naming amides, we follow the same pattern as we do for esters, except: Any alkyl groups attached to the nitrogen gets listed as “N-methyl”, “N-ethyl”, “N-propyl”, etc. The parent chain starts at the C=O (carbonyl) carbon and is counted moving away from the amide nitrogen. In the name, the parent chain’s ending “e” is replaced with “amide”. alkyl group attached to the nitrogen 4 3 2 1 N-methyl butanamide butanamide Naming Amides alkyl group attached to the nitrogen 4 5 2 3 1 N-ethyl pentanamide pentanamide alkyl group attached to the nitrogen 6 5 4 3 2 1 N-cyclopentyl -N-methyl hexanamide hexanamide methyl Naming Amides ethanamide (acetamide) N-methylpropanamide cyclopentane -carboxamide hexanamide N,N-dimethylcyclohexanecarboxamide Naming Acid Anhydrides When naming acid anhydrides, we: Determine the length of the chain on either side of the bridging oxygen. List both lengths alphabetically, replacing their ending “e” with “oic”. Write “anhydride” at the end of the name. 4 3 2 butanoic 1 1 2 ethanoic butanoic ethanoic anhydride Naming Acid Anhydrides ethanoic anhydride (acetic anhydride) Propanoic anhydride pentanoic propanoic anhydride Naming Nitriles When naming nitriles, we follow the rules for naming alkanes, except: The parent chain is the longest carbon chain that contains the nitrile carbon. We number the parent chain in the direction that gives the smallest number to the nitrile carbon. We add the suffix “nitrile” to the parent name. 1 5 4 3 2 pentanenitrile 1 4 3 2 butanenitrile 3 1 2 propanenitrile 1 2 ethanenitrile (acetonitrile) Monosubstituted Benzenes bromobenzene toluene anisole styrene chlorobenzene nitrobenzene ethylbenzene phenol aniline benzenesulfonic acid benzaldehyde benzoic acid benzonitrile Naming Substituted Benzenes When naming substituted benzenes: Identify the parent chain, which is the benzene containing the highest-priority functional group. That parent chain is the parent chain name. Highest priority Functional group (general formula) R = any CXHY chain Carboxylic acid (RCO2H) Ester (RCO2R') Acid chloride (RCOCl) Amide [R'C(O)NR2] Nitrile (R–C≡N) Ethanoic acid, propanoic acid, butanoic acid, etc. Ethyl ethanoate, methyl propanoate, etc. Ethanoyl chloride, propanoyl chloride N,N-dimethyl propanamide; N-ethylbutanamide Ethanenitrile, propanenitrile, etc. Alkoxycarbonyl Chloroformyl Amido Cyano Aldehyde ( ) Ethanal, propanal, butanal, etc. Oxo or formyl Ketone ( ) 2-butanone, 3-butanone, 2-pentanone Oxo Methanol, ethanol, propanol, etc. Hydroxy N,N-dimethylpropanamine, Nethylcyclohexanamine Amino Alcohol (ROH) Phenol (PhOH) Lowest priority Examples (if parent): If it’s a substituent to a higher-priority group, then it’s called: Amine (R'-NR2) Alkene ( Alkyne ( Ether (R'OR) Alkyl halide (RX) X = F, Cl, Br, or I Nitro (NO2) ) Ethene, propene, butene, etc. ) Ethyne, propyne, butyne, etc. Methoxyethane, ethoxypropane 2-bromopropane, 3-chlorobutane, etc. N/A methoxy, ethoxy, propoxy, etc. Fluoro, chloro, bromo, iodo, etc. Nitro Monosubstituted Benzenes bromobenzene toluene anisole styrene chlorobenzene nitrobenzene ethylbenzene phenol aniline benzenesulfonic acid benzaldehyde benzoic acid benzonitrile Naming Substituted Benzenes When naming substituted benzenes: Identify the parent chain, which is the benzene containing the highest-priority functional group. That parent chain is the parent chain name. The carbon atom in the ring that is attached to the priority functional group is numbered as carbon #1. Number around the ring in whichever direction (clockwise or counterclockwise) gives the lowest number at the first point of difference. If the numbers are the same in both directions, pick the one that gives the lower number to the substituent that is alphabetically first. Naming Polyfunctional Compounds When naming polyfunctional compounds: You must identify the highest-priority functional group. The parent chain containing this functional group is the parent chain name. Highest priority Functional group (general formula) R = any CXHY chain Carboxylic acid (RCO2H) Ester (RCO2R') Acid chloride (RCOCl) Amide [R'C(O)NR2] Nitrile (R–C≡N) Ethanoic acid, propanoic acid, butanoic acid, etc. Ethyl ethanoate, methyl propanoate, etc. Ethanoyl chloride, propanoyl chloride N,N-dimethyl propanamide; N-ethylbutanamide Ethanenitrile, propanenitrile, etc. Alkoxycarbonyl Chloroformyl Amido Cyano Aldehyde ( ) Ethanal, propanal, butanal, etc. Oxo or formyl Ketone ( ) 2-butanone, 3-butanone, 2-pentanone Oxo Methanol, ethanol, propanol, etc. Hydroxy N,N-dimethylpropanamine, Nethylcyclohexanamine Amino Alcohol (ROH) Phenol (PhOH) Lowest priority Examples (if parent): If it’s a substituent to a higher-priority group, then it’s called: Amine (R'-NR2) Alkene ( Alkyne ( Ether (R'OR) Alkyl halide (RX) X = F, Cl, Br, or I Nitro (NO2) ) Ethene, propene, butene, etc. ) Ethyne, propyne, butyne, etc. Methoxyethane, ethoxypropane 2-bromopropane, 3-chlorobutane, etc. N/A methoxy, ethoxy, propoxy, etc. Fluoro, chloro, bromo, iodo, etc. Nitro Naming Polyfunctional Compounds When naming polyfunctional compounds: You must identify the highest-priority functional group. The parent chain containing this functional group is the parent chain name. Once you identify the parent chain and its functional group, follow the naming rules for that particular functional group. All other functional groups in the molecule are considered and named as substituents. What Are Spiro Alkanes? Spiro alkanes are carbon/hydrogen molecules that have two or more rings fused together at single carbon points: Spiro[2.2]pentane Spiro[5.5]undecane Spiro[3.4]octane Spiro[4.5]decane Naming Spiro Alkanes IUPAC names for spiro alkanes have the format spiro[a.b]parent name. To name spiro alkanes: Count the total number of carbons across the entire molecule. This tells you the alkane parent name that goes at the end. Count the number of carbons to the left, and to the right of your spiro-carbon center. These numbers are a and b in your IUPAC name, listed from lowest to highest. Write your final IUPAC name as spiro[a.b]parent name. What Are Bicyclic Alkanes? Bicyclic alkanes are carbon/hydrogen molecules that have two or more rings fused together across multi-carbon “bridges”. These bridging carbons are called bridgehead carbons. Bicyclo[1.1.0]butane Bicyclo[4.3.0]nonane Bicyclo[3.3.0]octane Bicyclo[3.2.0]heptane What Are Bicyclic Alkanes? Bicyclic alkanes are carbon/hydrogen molecules that have two or more rings fused together across multi-carbon “bridges”. These bridging carbons are called bridgehead carbons. Bicyclo[2.2.1]heptane Bicyclo[3.2.1]octane Bicyclo[1.1.1]pentane Naming Bicyclic Alkanes IUPAC names for bicylic alkanes have the format bicyclo[a.b.c]parent name. To name bicylic alkanes: Count the total number of carbons across the entire molecule. This tells you the alkane parent name that goes at the end. Count the number of carbons to the left, and to the right, and above your bridgehead carbons. These numbers are a, b, and c in your IUPAC name, listed from HIGHEST to lowest (the opposite of spiro alkanes). Write your final IUPAC name as bicyclo[a.b.c]parent name.