Question

Name each alkane. (a) \(\mathrm{H}_{3} \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}\) (b) CCC(C)C (c) CCC(CC)CC(C)C (d) CCC(C)(C)CC

Short answer

(a) Pentane, (b) 2-Methylbutane, (c) 3,5-Dimethylhexane, (d) 2,2,3-Trimethylpentane

Step-by-step solution

- Identify Number of Carbon Atoms

Count the number of carbon atoms in the longest continuous chain to determine the base name for the alkane. For branched alkanes, translate the SMILES notation into the structural formula if needed before counting.

- Determine Alkane Name

Using the number of carbon atoms determined in Step 1, name the alkane according to the standard nomenclature rules: Meth- (1 C), Eth- (2 C's), Prop- (3 C's), But- (4 C's), Pent- (5 C's), Hex- (6 C's), etc. Append the suffix '-ane' for alkanes.

- Identify Substituents and Numbering

For branched alkanes, identify any alkyl substituents and their position on the main carbon chain. Use the lowest possible numbers when assigning locations to the substituents.

- Name Branched Alkanes

Combine the base name from Step 2 with the substituent names and corresponding numbers from Step 3. Arrange substituents alphabetically, and use prefixes di-, tri-, etc., if the same substituent occurs more than once.

- Name Each Alkane

(a) A straight chain of five carbon atoms is named pentane. (b) After translating the SMILES, the alkane has a four-carbon chain with a methyl group on the third carbon, so it's named 2-methylbutane. (c) The longest chain contains six carbon atoms, with a methyl group on the third and fifth carbons, so it is named 3,5-dimethylhexane. (d) The longest chain contains five carbon atoms, with two methyl groups on the second carbon and another on the third, so it is named 2,2,3-trimethylpentane.

Key concepts

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) nomenclature is the standardized system for naming chemical compounds, primarily used in organic chemistry. The basic principle of IUPAC naming is to provide a unique and unambiguous name for each compound, which accurately describes its structure. For alkanes, the IUPAC nomenclature involves identifying the longest carbon chain to determine the alkane's base name and then adding prefixes and suffixes to indicate the presence and positioning of any branches or substituents.

Using a combination of prefixes that denote the number of carbon atoms - like Meth- (1 carbon), Eth- (2 carbons), and so on, and adding the suffix '-ane' for alkanes, helps one to construct the name of the simplest straight-chain alkanes. When naming branched alkanes, additional rules apply, such as numbering the carbon atoms to position substituents and arranging substituent names alphabetically.

Organic Chemistry

Organic chemistry is the study of the structure, properties, composition, and reactions of organic compounds, which contain carbon. Alkanes are one of the primary topics in organic chemistry, as they form the basis for more complex organic molecules. These hydrocarbons contain only carbon and hydrogen atoms, with single bonds between the carbon atoms, making them saturated compounds.

Understanding alkanes involves more than just naming them; it includes knowing their physical and chemical properties, reactions, and how they interact with other molecules. This field of chemistry is fundamental not only in academic education but also in numerous industries, including pharmaceuticals, petrochemicals, and materials science. Students often encounter alkanes early in their studies as they present a clear model for learning about molecular structure and bonding.

Structural Formula

The structural formula represents the molecular structure of a compound, showing how atoms are arranged and bonded together. It is more informative than a simple molecular formula because it provides a visual depiction of the molecule's geometry. When naming alkanes, the structural formula is invaluable as it illustrates the carbon chain's length, the location of any branches or substituents, and the presence of multiple substituents.

In organic chemistry, there are different ways to represent structures, such as the full structural formula, which includes every bond and atom, and the condensed structural formula, which simplifies the visualization by grouping certain atoms together. Structural formulas play a crucial role in the understanding of organic molecules and are a key tool for solving naming problems in IUPAC nomenclature.

SMILES Notation

SMILES (Simplified Molecular Input Line Entry System) notation is a way to describe the structure of chemical molecules using short ASCII strings. SMILES provides a compact encoding of molecular information and can be used to convert to two-dimensional and three-dimensional molecular models. It is especially useful in cheminformatics software and for enabling the digital search and cataloging of compounds.

When you come across a SMILES notation, understanding it is useful for translating it into a traditional structural formula. For instance, the 'C' in SMILES denotes a carbon atom, parentheses are used for branching, and numbers indicate the location of cyclic structures. Learning to interpret SMILES notation is an important skill in modern organic chemistry, complementing traditional methods of representing molecular structures.