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Mastering the Naming of Amines: IUPAC and Common Nomenclature Explained

Naming Primary Amines: The IUPAC Rules and

Common Nomenclature

Have you ever wondered how chemists name primary amines? There are two main systems used: systematic nomenclature (IUPAC rules) and common nomenclature.

In this article, we will explore both systems, their rules, and examples.

Systematic Nomenclature (IUPAC Rules)

The International Union of Pure and Applied Chemistry (IUPAC) has established a set of guidelines for systematically naming organic compounds. The IUPAC rules prioritize the longest continuous carbon chain, which forms the backbone of the molecule.

Let’s take a look at the IUPAC rules for naming primary amines. Step 1: Identify the longest continuous carbon chain that includes the nitrogen atom.

The parent chain must contain the amino group (NH2) as one of its substituents. We then change the -e suffix of the parent chain to -amine.

Step 2: Number the carbon atoms in the parent chain, starting from the end nearest to the amino group. The nitrogen atom is given the lowest number possible.

If there are other functional groups, they are assigned numbers that give them the lowest possible set of numbers. The carbon chain is numbered in the direction that gives the other substituents the lowest possible combination of numbers.

Step 3: Indicate the location of each substituent by giving its number and name. The substituents are named alphabetically, and the prefixes di, tri, tetra, etc., are used to indicate multiple identical substituents.

Examples:

1. CH3NH2 (methylamine)

The parent chain is one carbon long, and it contains the amino group.

The -e suffix of the parent chain is changed to -amine. 2.

CH3CH2NH2 (ethylamine)

The parent chain is two carbon long, and the amino group is attached to the first carbon atom. The -e suffix of the parent chain is changed to -amine.

3. CH3CH2CH2NH2 (propylamine)

The parent chain is three carbon long, and the amino group is attached to the first carbon atom.

The -e suffix of the parent chain is changed to -amine. 4.

CH3CH2CH2CH2NH2 (butylamine)

The parent chain is four carbon long, and the amino group is attached to the first carbon atom. The -e suffix of the parent chain is changed to -amine.

5. CH3CH2CH2CH2CH2NH2 (pentylamine)

The parent chain is five carbon long, and the amino group is attached to the first carbon atom.

The -e suffix of the parent chain is changed to -amine.

Common Nomenclature

The common nomenclature (also known as trivial nomenclature) is an informal naming system where the substituent groups are given a name based on their structure or from other compounds with similar structures. Common nomenclature is used mainly for simple compounds and is not used in more complex or systematic compounds.

The most common method of naming primary amines under the common nomenclature is to add the -yl ending to the name of the parent alkane, followed by the word amine. If the amino group is part of a ring, then the prefix N- is used before the alkyl group.

Examples:

1. CH3NH2 (methylamine)

The substituent is methyl, so we add -yl to methyl, giving us meth- + -yl = methyl.

The final name is methylamine. 2.

CH3CH2NH2 (ethylamine)

The substituent is ethyl, so we add -yl to ethyl, giving us eth- + -yl = ethyl. The final name is ethylamine.

3. CH3CH2CH2NH2 (propylamine)

The substituent is propyl, so we add -yl to propyl, giving us prop- + -yl = propyl.

The final name is propylamine. 4.

CH3(CH2)3NH2 (butylamine)

The substituent is butyl, so we add -yl to butyl, giving us but- + -yl = butyl. The final name is butylamine.

Naming a Compound Where the Amino group is Not the Highest Priority

Sometimes, the amino group is not the highest priority functional group in the compound. In such cases, we use the prefix “amino” followed by the name of the group having the highest priority.

Here are some examples:

1. CH3NHCH2OH (2-aminoethanol)

The amino group (-NH2) and the hydroxy group (-OH) are present in this compound.

The hydroxy group is higher in priority than the amino group. Hence we name the compound as 2-aminoethanol, where the amino group is prefixed.

2. CH3NHCH2COOH (2-aminoacetic acid)

The amino group (-NH2) and carboxylic group (-COOH) are present in this compound.

Carboxylic group takes priority over the amino group. Hence we name the compound as 2-aminoacetic acid.

In conclusion, naming primary amines can be tricky, but it follows a systematic approach that requires knowledge about the location of the nitrogen atom and its substituents. Both systematic nomenclature and common nomenclature are used for naming primary amines.

Specific conditions, such as low priority of amino groups might arise while naming primary amines, which necessitates prefixing the compound name with amino. With this knowledge, you can now confidently name primary amines with ease.

3) Naming Secondary and Tertiary Amines: Identical or

Different Alkyl Groups

Naming secondary and tertiary amines (amines with two or three alkyl or aryl groups, respectively) follow similar rules as primary amines, but with the added complexity of having multiple substituents. The prefixes used to name these amines depend on the number and type of substituents present.

Identical Alkyl Groups

When the alkyl (or aryl) groups on a secondary or tertiary amine are identical, the prefixes used are di- and tri-. Here are some examples:

1.

(CH3)2NH (dimethylamine)

The amine molecule has two methyl (CH3) groups, so we use the prefix di-. The final name is dimethylamine.

2. (CH3)3N (trimethylamine)

The amine molecule has three methyl groups, so we use the prefix tri-.

The final name is trimethylamine.

Different Alkyl Groups

When the alkyl (or aryl) substituents on a secondary or tertiary amine are different, we use the N- prefix to indicate the nitrogen atom’s attachment site for the substituents. The substituents are then named alphabetically based on their prefixes.

Here are some examples:

1. CH3NHCH2CH3 (N-methylethylamine)

The amine molecule has a methyl (CH3) and ethyl (CH2CH3) substituent.

We use N- to indicate the nitrogen’s position and prefix the substituents accordingly, giving us N-methylethylamine. 2.

(CH3)2NCH2CH3 (N,N-dimethylpropylamine)

The amine molecule has two methyl (CH3) and one propyl (CH2CH2CH3) substituents. We use N- to indicate the nitrogen’s position and prefix the substituents alphabetically.

The final name is N,N-dimethylpropylamine. 4) Aromatic and Other Common Amines: Common Names

Aromatic amines and other common amines are named using common names rather than IUPAC or systematic naming systems.

These compounds are often found naturally occurring in organic bases, amino acids, alkaloids, and synthetic medicines. Aromatic amines are named according to the group attached to the benzene ring followed by the word “amine.” For example, aniline (C6H5NH2) is a common aromatic amine where the benzene ring is attached to an amino group.

Common amines found in organic bases, amino acids, and alkaloids are often named based on their common names in the scientific field. For instance, tyramine (C8H11NO) is a common amine found in fermented foods and plants.

It is named based on the tyrosine amino acid, from which it is found to be derived. Synthetic medicines that contain amines are typically given trade names.

Some of the most commonly used amines in synthetic medicine include chlorpheniramine, a first-generation antihistamine used to treat allergies, and phenylephrine, a decongestant used to alleviate nasal congestion. These compounds are often prescribed under different trade names across continents.

In summary, secondary and tertiary amines are named based on the prefixes used for identical and different alkyl (or aryl) groups. Aromatic and common amines are typically referred to using common names, trade names, or names borrowed from scientific fields such as organic chemistry and biochemistry.

A deep understanding of fundamental organic chemistry concepts is paramount to naming compounds, a critical skill for chemists and students alike. In conclusion, the naming of amines follows specific guidelines depending on the amine’s type and substituents.

Primary, secondary, and tertiary amines have different naming conventions, with primary amines having both a systematic and common naming system. Identical and different alkyl groups affect the prefixes used in secondary and tertiary amines.

Aromatic and common amines are typically referred to using common names, trade names, or names borrowed from scientific fields. The correct naming of amines is crucial in chemistry, and an understanding of these concepts is essential for scientists and students in the field.

FAQs:

1. What is the IUPAC rule for naming primary amines?

Ans: Identify the longest continuous carbon chain that includes the nitrogen atom, change the -e suffix of the parent chain to -amine, and number the carbon atoms in the parent chain starting from the end nearest to the amino group.

2.

How are secondary and tertiary amines named when the alkyl groups are identical? Ans: Secondary and tertiary amines with identical alkyl groups are named using the prefixes di- and tri.

3. What is the prefix for referring to different alkyl groups in secondary and tertiary amines?

Ans: The prefix N- is used to indicate the nitrogen atom’s attachment site for the substituents. 4.

How are aromatic amines named? Ans: Aromatic amines are named according to the group attached to the benzene ring, followed by the word “amine.”

5.

What are some common amines found in organic bases, amino acids, and alkaloids? Ans: Examples of common amines in organic bases include tyramine, while amino acids can contain a variety of different amines, and alkaloids such as morphine contain nitrogen atoms.

6. What is the importance of correctly naming amines in chemistry?

Ans: Correctly naming amines is crucial in chemistry since this is essential for accurately describing and understanding organic compounds.

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