Problem 18 - Chemistry The Central Science In Si Units

Question

Give the name or condensed structural formula, as appropriate: (a) 3-phenylpentane (b) 2,3 -dimethylhexane (c) 3,3-dimethyloctane (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right) \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\)

Step-by-Step Solution

Answer

(a) \( \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{C}(\mathrm{C}_6\mathrm{H}_5)\mathrm{HCH}_2\mathrm{CH}_3 \); (b) \( \mathrm{CH}_{3}\mathrm{CH}(\mathrm{CH}_3)\mathrm{CH}(\mathrm{CH}_3)\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3 \); (c) \( \mathrm{CH}_{3}\mathrm{CH}_2\mathrm{CH}(\mathrm{CH}_3)_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3 \); (d) 3,5-dimethylhexane.

Step 1: Understand the Structure

Before giving names or condensed formulas, start by understanding the structure of each compound given, allowing you to determine either its name or structural formula efficiently.

Step 2: Analyze 3-phenylpentane

3-phenylpentane consists of a pentane chain with a phenyl group (a benzene ring as a substituent) attached to the third carbon. The condensed structural formula is: \( \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{C}(\mathrm{C}_6\mathrm{H}_5)\mathrm{HCH}_2\mathrm{CH}_3 \).

Step 3: Analyze 2,3-dimethylhexane

2,3-dimethylhexane consists of a hexane chain with methyl groups attached to the second and third carbon atoms. The condensed structural formula is: \( \mathrm{CH}_{3}\mathrm{CH}(\mathrm{CH}_3)\mathrm{CH}(\mathrm{CH}_3)\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3 \).

Step 4: Analyze 3,3-dimethyloctane

3,3-dimethyloctane is an octane chain with two methyl groups attached to the third carbon atom. The condensed structural formula is: \( \mathrm{CH}_{3}\mathrm{CH}_2\mathrm{CH}(\mathrm{CH}_3)_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3 \).

Step 5: Name the Given Structural Formula

For the compound \( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}(\mathrm{CH}_{3}) \mathrm{CH}_{2} \mathrm{CH}(\mathrm{CH}_{3})_{2} \), identify the longest chain and substituents. It has a six-carbon chain (hexane) with methyl groups on the third and fifth carbons, naming it 3,5-dimethylhexane.

Key Concepts

Understanding Nomenclature in Organic Chemistry

In the vast world of organic chemistry, nomenclature refers to the system we use to name chemical compounds. This intricate naming process is vital for the clear communication and identification of various chemical species. In organic chemistry:

• It helps scientists convey information succinctly and accurately without lengthy descriptions.
• Naming starts with recognizing the longest continuous chain of carbon atoms, known as the parent chain.
• For each compound, substituents or side groups branch off from the main chain, and these affect the name.

Knowing how to determine the proper IUPAC name requires understanding the priority of functional groups and the correct positioning of numbers and prefixes in the name. By writing the structure step by step, as in the examples given, where compounds are analyzed structurally first, an accurate systematic name can be assigned.

Introduction to Organic Chemistry

Organic chemistry is a branch of chemistry dedicated to the study of carbon-containing compounds. These compounds make up the basis of all life on earth, as carbon is incredibly versatile:

• Carbon atoms can form four covalent bonds, allowing for various structures.
• The ability of carbon atoms to bond in chains and rings creates the diversity seen in organic compounds.
• Organic chemistry encompasses molecules with additional elements such as hydrogen, oxygen, nitrogen, and halogens.

Understanding how to read and construct chemical formulas and names in organic chemistry is crucial for anyone studying this field. It allows chemists to deduce the structure and potential reactivity of molecules, which has profound implications in fields like pharmacology, biochemistry, and industrial chemistry.

The Role of Alkanes in Organic Chemistry

Alkanes are a fundamental class of hydrocarbons in organic chemistry, characterized by single bonds between carbon atoms:

• They are saturated hydrocarbons, meaning they have the maximum number of hydrogen atoms attached to each carbon atom.
• The general formula for alkanes is \( C_nH_{2n+2} \), where \( n \) is the number of carbon atoms.
• Alkanes are relatively non-reactive due to the strength of the carbon-carbon and carbon-hydrogen bonds.

In the exercise, we see alkanes like hexane and octane, which act as the backbone structures from which substituents branch off. These body chains are what we primarily look for when determining the name in nomenclature practice. Alkanes play a crucial role in numerous applications including fuels, lubricants, and as starting materials for other chemical syntheses.