Functional Groups and IUPAC Flashcards
What’s the difference between amides, imides, amines, and enamines? How do you name an organic compound with multiple functional groups? Use these cards to master functional groups and IUPAC conventions, and you’ll gain a solid foundation for your further review of MCAT organic chemistry.
Briefly describe how to name an organic compound according to the IUPAC nomenclature scheme.
- Identify the molecule’s principal functional group.
- Find the longest carbon chain containing that group.
- Number that chain, starting from the end that gives the principal functional group the lowest possible number.
- Name all other functional groups according to this numbering scheme.
What are the prefixes for carbon chains consisting of one and two carbons, respectively?
- One-carbon chains are given the prefix “meth-”.
- Two-carbon chains are given the prefix “eth-”.
What are the prefixes for carbon chains consisting of three and four carbons, respectively?
- Three-carbon chains are given the prefix “prop-”.
- Four-carbon chains are given the prefix “but-”.
What are the prefixes for carbon chains consisting of five and six carbons, respectively?
- Five-carbon chains are given the prefix “pent-”.
- Six-carbon chains are given the prefix “hex-”.
What are the prefixes for carbon chains consisting of seven and eight carbons, respectively?
- Seven-carbon chains are given the prefix “hept-”.
- Eight-carbon chains are given the prefix “oct-”.
What is an alkane?
It is an organic molecule consisting of carbon and hydrogen atoms, connected only by single bonds.
All alkanes are named with the suffix “-ane” and a prefix determined by the number of carbons in the chain. The three-carbon chain above is called “propane.”
What is the name of this molecule?
pentane
To name an alkane, first isolate the chain that contains the highest-priority functional group. Identify the prefix based on the number of carbons in that chain, then attach the “-ane” suffix.
What is the name of this molecule?
2-methylpropane (isobutane)
Historically, alkane chains that are branched at the second carbon have been named with the “iso-“ prefix. This denotes that 2-methylpropane is a structural isomer of butane. While you may see this in passages, it is rarely tested directly on the MCAT, since the IUPAC has moved away from that naming convention.
What is an alkene?
It is an organic molecule consisting of carbon and hydrogen atoms and containing at least one carbon-carbon double bond.
All alkenes are named with the suffix “-ene” and a prefix determined by the number of carbons in the chain. The three-carbon chain above is called “propene.”
What is the name of this molecule?
2-butene
To name an alkene, first isolate the chain that contains the highest-priority functional group. Identify the prefix based on the number of carbons in that chain, then attach the “-ene” suffix. Note that the suffix must be paired with the number of the lowest-numbered carbon participating in the double bond.
What is an alkyne?
It is an organic molecule consisting of carbon and hydrogen atoms and containing at least one carbon-carbon triple bond.
All alkynes are named with the suffix “-yne” and a prefix determined by the number of carbons in the chain. The three-carbon chain above is called “propyne.”
What is the name of this molecule?
1-butyne
To name an alkyne, first isolate the chain that contains the highest-priority functional group. Identify the prefix based on the number of carbons in that chain, then attach the “-yne” suffix. Note that the suffix must be paired with the number of the lowest-numbered carbon participating in the triple bond.
What is the principal functional group in this molecule?
amine (-NH2) group
In this molecule, 1-propanamine, -NH2 is the only functional group attached to the main carbon chain.
What is the principal functional group in this molecule?
alcohol (-OH) group
In general, oxygen-containing groups take priority in nomenclature. The more bonds to oxygen in the functional group, the higher its priority. This molecule, 1-amino-2-propanol, has the “-ol” ending to indicate that the alcohol has highest priority even though the amino group is on the first carbon.
In the molecule below, at what numbered position does the highest-priority functional group reside?
The -OH is at carbon 1 (the terminal carbon).
Carbon chains are numbered to give the highest-priority functional group the lowest possible number. When a high-priority group is at the end of the chain, it is in the 1 position by default. In other words, this is always called 1-butanol, never 4-butanol.
In the molecule below, at what numbered position does the highest-priority functional group reside?
The highest-priority group (-OH) is at carbon 2.
Remember that oxygen-containing functional groups take priority over nitrogen-containing groups. The chain is numbered so that the -OH group resides at the lowest possible numerical position, making this molecule 4-amino-2-butanol.
In the molecule below, at what numbered position does the Cl atom reside?
carbon 3
Carbon chains are always numbered so that the highest-priority functional group gets the lowest possible number. In this molecule, 3-chloro-1-butanol, the -OH has the highest priority and must be given position 1.
In the molecule below, at what numbered position does the Cl atom reside?
carbon 3
With cyclic carbon chains, continue to ensure that the highest-priority group gets the lowest possible number. Here, numbering must begin at the carbon with the -OH group. Next, continue to label in the direction that results in the lowest possible number for the remaining functional groups. This molecule is 3-chlorocyclohexanol; it would never be called 5-chlorocyclohexanol.
What is an alcohol?
It is an organic molecule with an -OH as its highest-priority functional group.
All alcohols are named with the suffix “-ol” and a prefix determined by the number of carbons in the chain. The molecule above is propanol.
What is the name of this molecule?
2-butanol
To name an alcohol, first identify the prefix based on the number of carbons in the chain that contains the -OH functional group. Next, attach the “-ol” suffix, along with the lowest number that could possibly apply to the -OH position. In other words, this would never be called 3-butanol.
What is the name of this molecule?
phenol (benzenol)
While the second name follows the IUPAC system more closely, phenol is the name that will appear on the MCAT. As the name implies, it consists of a phenyl group (-C6H5) attached to an -OH group.
What is an aldehyde?
It is an organic molecule consisting of an alkane chain with a carbon-oxygen double bond on one of the chain’s terminal carbons.
All aldehydes are named using the suffix “al.” The three-carbon chain above is called “propanal.”
What is the name of this molecule?
pentanal
To name an aldehyde, remove the “-e” from the end of the name of the parent alkane and replace it with “-al.” Since an aldehyde is a terminal group, it is unnecessary to write 1-pentanal.
What is a ketone?
It is an organic molecule consisting of an alkane chain with a carbon-oxygen double bond on one of the internal carbons of the chain.
All ketones are named using the suffix “-one.” The three-carbon chain above is called propanone, commonly known as acetone.
What is the name of this molecule?
2-pentanone
To name a ketone, remove the “-e” from the end of the name of the parent alkane and replace it with “-one.” This molecule is always called 2-pentanone, never 4-pentanone.
What is a carboxylic acid?
It is an organic molecule consisting of an alkane chain with a carbon-oxygen double bond and a hydroxyl (-OH) on one of the chain’s terminal carbons. This group is sometimes written as “COOH.”
All carboxylic acids are named by removing the “-e” from the end of the name of the parent alkane and replacing it with “-oic acid.” The three-carbon chain above is called “propanoic acid.”
What is the name of this molecule?
butanoic acid
To name a carboxylic acid, remove the “-e” from the end of the name of the parent alkane and replace it with “-oic acid.”
What is a dicarboxylic acid?
It is a molecule that contains two carboxylic acid functional groups.
If the molecule is a chain (rather than a ring), the acids will be found at both ends of the chain. The molecule above is called “propanedioic acid.”
What is an acyl chloride?
It is a carboxylic acid derivative in which the -OH has been replaced by a -Cl.
All acid chlorides are named by removing “-oic acid” from the end of the name of the parent carboxylic acid and replacing it with “-oyl chloride.” The three-carbon chain above is called “propanoyl chloride.”
What is the name of this molecule?
pentanoyl chloride
To name an acid chloride, remove “-oic acid” from the end of the name of the parent carboxylic acid and replace it with “-oyl chloride.”
What is an acid anhydride?
It is the result of the dehydration (loss of H2O) of two carboxylic acid molecules. It consists of two carbonyls separated by an oxygen atom.
Acid anhydrides are named by adding “-oyl” to the name of the first acid group and “-oate” to the other. The molecule above is called “propanoyl propanoate,” commonly known as “propanoic anhydride” since both acids are the same.
What is the name of this molecule?
pentanoyl pentanoate (pentanoic anhydride)
To name an acid anhydride, add “-oyl’“to the name of the first acid group and “-oate” to the other. When both groups come from identical carboxylic acids, it’s common to see the name of that acid with “anydride” attached.
What is an amide?
It is a carboxylic acid derivative in which the -OH has been replaced by an -NH2.
All amides are named by removing “-oic acid” from the end of the name of the parent carboxylic acid and replacing it with “-amide.” The three-carbon chain above is called “propanamide.”
What is the name of this molecule?
hexanamide
To name an amide, remove “-oic acid” from the end of the name of the parent carboxylic acid and replace it with “-amide.”
What is an ester?
It is a carboxylic acid derivative in which the -OH has been replaced by an -OR group. R is used to denote a hydrocarbon chain.
Esters are named by adding the “-yl” suffix to the alkane chain not on the carbonyl side of the single-bonded oxygen. The “-oate” suffix is then added to the chain on the carbonyl side. The molecule above is called “propyl ethanoate.”
What is the name of this molecule?
ethyl pentanoate
Esters are named by adding the “-yl” suffix to the alkane chain not on the carbonyl side of the single-bonded oxygen. The “-oate” suffix is then added to the chain on the carbonyl side.
What is a β-keto carboxylic acid?
It is a carboxylic acid molecule with a carbonyl at the beta position. Remember, the alpha position is the carbon adjacent to the carbonyl carbon, while the beta position is one carbon more distant than that.
The molecule above is called “β-keto butanoic acid.”
What is an amine?
It is an organic molecule consisting of an alkane chain with an -NH2 functional group.
Amines are named by replacing the “-e” suffix from the parent alkane chain with “-amine.” The three-carbon molecule above is called propanamine or propylamine.
What is the name of this molecule?
butanamine
Amines are named simply using the suffix “-amine.”
What is the name of this functional group?
phenyl
A phenyl functional group is simply a benzene ring (C6H5) bound directly to the rest of the molecule.
What is the name of this functional group?
benzyl
Be sure to remember that a benzyl functional group is not simply a benzene ring! It consists of that ring (C6H5) bound to a CH2 group. In other words, a benzyl group is a phenyl group with one additional carbon.
What is the name of this functional group?
nitro functional group (-NO2)
Nitro groups contain resonance and are known for their electron-withdrawing effects.
What is a thiol?
It is an organic molecule. It is chemically similar to an alcohol, but has the -OH replaced with an -SH group.
Since sulfur is in the same group as oxygen, thiols and alcohols have similar chemical properties. In general, the prefix “thio-“ indicates “sulfur-containing.”
What is an ether?
It is an organic molecule with two alkane chains, both single-bonded to the same oxygen atom.
Ethers are named according to the alkane chains bonded to the oxygen. Since both chains in the molecule above consist of two carbons, this compound is known as diethyl ether.
What is an acetal?
It is an aldehyde derivative in which the carbonyl has been replaced by two -OR groups. Note that the R groups can be identical or different.
Acetals are formed via the reaction of an aldehyde molecule with two alcohol equivalents. They are often tested on the MCAT in connection to carbohydrates (sugars).
What is a ketal?
It is a ketone derivative in which the carbonyl has been replaced by two -OR groups. Note that the R groups can be identical or different.
Ketals are formed via the reaction of a ketone molecule with two alcohol equivalents.
What is the name of this functional group?
imine
Imine nomenclature is rarely tested on the MCAT. You should simply be able to identify a carbon-nitrogen double bond as an imine.
What is the name of this functional group?
nitrile
Nitrile nomenclature is rarely tested on the MCAT. You should simply be able to identify a carbon-nitrogen triple bond as a nitrile.
