Question

Write structural formulas for the following compounds. (a) 2 -methylpropane (b) 3,3 -diethyl-2-methylpentane (c) 2,4-dimethyloctane (d) 3 -ethyl-3-methylhexane

Short answer

(a) 2 -methylpropane: \( CH_3 - CH(CH_3) - CH_3 \) (b) 3,3 -diethyl-2-methylpentane: \( CH_3 - CH(CH3) - CH(C_2H_5)(C_2H_5) - CH_2 - CH_3 \) (c) 2,4-dimethyloctane: \( CH_3 - CH(CH_3) - CH_2 - CH(CH_3) - CH_2 - CH_2 - CH_2 - CH_3 \) (d) 3 -ethyl-3-methylhexane: \( CH_3 - CH_2 - CH(CH_3)(C_2H_5) - CH_2 - CH_2 - CH_3 \)

Step-by-step solution

Structural Formula for 2 -methylpropane

2 -methylpropane or isobutane is a type of alkane with a branched-chain. It has four carbons, hence the 'propane', and a 'methyl' branch on the second carbon. Draw three carbons in a row to represent the propane, and then branch a methyl from the second carbon. This gives the structure: \[ CH_3 - CH(CH_3) - CH_3 \].

Structural Formula for 3,3 -diethyl-2-methylpentane

3,3 -diethyl-2-methylpentane is a type of alkane with two 'ethyl' branches on the third carbon and a 'methyl' branch on the second carbon. Draw five carbons in a row to represent the pentane. Add two ethyl branches on the third carbon and one methyl on the second carbon. This gives the structure: \[ CH_3 - CH(CH3) - CH(C_2H_5)(C_2H_5) - CH_2 - CH_3 \].

Structural formula for 2,4-dimethyloctane

2,4-dimethyloctane is an alkane with 'methyl' branches on the second and fourth carbons. Draw eight carbons in a row to represent the octane. Then, add a methyl branch on the second and fourth carbons. The structure will be: \[ CH_3 - CH(CH_3) - CH_2 - CH(CH_3) - CH_2 - CH_2 - CH_2 - CH_3 \].

Structural formula for 3 -ethyl-3-methylhexane

3 -ethyl-3-methylhexane is an alkane with 'ethyl' and 'methyl' branches on the third carbon. Draw six carbons in a row to represent the hexane. Then, add a methyl and ethyl branch on the third carbon. The structure will be: \[ CH_3 - CH_2 - CH(CH_3)(C_2H_5) - CH_2 - CH_2 - CH_3 \].

Key concepts

Organic Chemistry

Organic chemistry is the branch of chemistry that focuses on the study of carbon-containing compounds. Carbon is a versatile element capable of forming stable bonds with many other elements, leading to the vast diversity of organic compounds. This area of chemistry explores everything from small molecules to large, complex structures like proteins and polymers. Organic chemistry is foundational because:

• It helps us understand the structure and behavior of molecules in living organisms.
• It is essential for developing pharmaceuticals, plastics, fuels, and many everyday materials.
• It includes functional groups that define how molecules react.

Leaning on carbon's ability to form chains and rings, organic chemistry can describe the intricate details of how atoms bond to form diverse compounds.

Alkanes

Alkanes are the simplest form of hydrocarbons, composed exclusively of carbon and hydrogen atoms connected by single bonds. This saturation of single bonds makes them "saturated" hydrocarbons. They are also known as paraffins.Alkanes have fundamental properties:

• They are relatively non-reactive compared to other organic compounds because of their strong C-C and C-H bonds.
• They follow the general formula of \[ C_nH_{2n+2} \] where \( n \) is the number of carbon atoms.
• They are a major component of natural gas and crude oil.

The ability of carbon to form branched structures adds variety to alkanes, transitioning from simple chains to more complex configurations.

Branched-Chain Hydrocarbons

Branched-chain hydrocarbons are alkanes that include side chains branching off from the main carbon chain. These branches alter the chemical and physical properties of the molecule by changing its shape. This affects characteristics like boiling and melting points.Features of branched chains:

• Branches are typically shorter hydrocarbon chains or groups such as "methyl" \((CH_3)\) or "ethyl" \((C_2H_5)\).
• They can make molecules more compact and affect the molecule's symmetry.
• Branches can influence a compound's reactivity and solubility.

For example, 2-methylpropane is a branched-chain alkane, as it has a "methyl" group attached to the primary carbon chain. This contrast in structure from straight-chain alkanes can lead to significant variances in properties between isomers.

IUPAC Nomenclature

IUPAC nomenclature is a systematic way of naming organic chemical compounds based on their structure. It ensures consistency and clarity in chemical communication. The International Union of Pure and Applied Chemistry (IUPAC) sets these naming standards. Key rules of IUPAC nomenclature for alkanes:

• Identify the longest continuous carbon chain and base the parent name on this chain.
• Number the carbon atoms in the main chain from the end nearest to a branch.
• Name and number all the branches substituting the primary carbon chain and use prefixes like 'methyl-', 'ethyl-', 'di-', 'tri-' etc.
• Combine the elements of the name into a single word: the name of the branches (with numbers indicating the branches' positions) followed by the name of the main chain.

By following these conventions, names convey important structural information about organic molecules, which reflects deeply on the science's precision and universality across different languages and regions.