Question

Draw the condensed structural formula for each of the following compounds: (a) 2-methylpropane (b) 2,2 -dimethylbutane (c) 3-ethylheptane (d) 3,3 -diethylpentane

Short answer

(a) CH₃CH(CH₃)CH₃, (b) (CH₃)₃CCH₂CH₃, (c) CH₃CH₂CH(CH₂CH₃)CH₂CH₂CH₂CH₃, (d) CH₃CH₂C(CH₂CH₃)₂CH₂CH₃

Step-by-step solution

Understand the Nomenclature

Each name given is an IUPAC name detailing the structure of the organic compound. Break down the name to understand how many carbon atoms and what branches or substituents (methyl, ethyl) are involved.

Identify the Parent Chain

Identify the longest continuous chain in each compound. This chain determines the base name (propane, butane, heptane, pentane) and the number of carbon atoms present in a straight line.

Locate the Substituents

Locate the carbon atom(s) which should possess a substituent. The prefix like '2-methyl' in 2-methylpropane tells us the methyl group (CH₃) is on the second carbon of the longest chain. Similarly, '3-ethyl' in 3-ethylheptane implies an ethyl group is attached to the third carbon.

Draw Condensed Structural Formulas

For each compound, draw the structural formula using alkyl groups and connect them based on the locations identified. (a) For 2-methylpropane: CH₃CH(CH₃)CH₃ (b) For 2,2-dimethylbutane: (CH₃)₃CCH₂CH₃ (c) For 3-ethylheptane: CH₃CH₂CH(CH₂CH₃)CH₂CH₂CH₂CH₃ (d) For 3,3-diethylpentane: CH₃CH₂C(CH₂CH₃)₂CH₂CH₃ Make sure each carbon atom forms four bonds either with hydrogen or other carbon atoms.

Key concepts

IUPAC Nomenclature

IUPAC Nomenclature provides a systematic way of naming organic chemical compounds. This system helps in clearly identifying the number of carbon atoms, the position of substituents, and the type of compound. Consider a name like 2-methylpropane. The 'propane' part indicates that the main carbon chain consists of three carbon atoms, forming a linear backbone. The prefix 'methyl' tells us there is a CH₃ group attached. The number '2' indicates that this group is attached to the second carbon of the main chain.

• "Meth-" refers to one carbon atom
• "Eth-" refers to two carbon atoms
• "Prop-" refers to three carbon atoms
• "But-" refers to four carbon atoms

Understanding these roots and prefixes allows chemists to visualize molecules without needing to see their structural formulae directly. Each substituent's number placement in the name ensures they are positioned on the correct carbon, maintaining standard naming conventions across similar compounds.

Condensed Structural Formula

A condensed structural formula provides a compact representation of a molecule, highlighting how atoms are connected. In drawing these formulas, recognize individual groupings of atoms like methyl (CH₃), ethyl (C₂H₅), etc., and their connections.
For example, when drawing 2-methylpropane, note how each methyl group is attached to the central carbon. Write this as CH₃CH(CH₃)CH₃, putting the methyl group in brackets to show its direct connection to the previous carbon. This representation condenses multiple atoms into concise grouping.

• Methyl group: CH₃
• Ethyl group: CH₂CH₃
• Direct connections emphasized by placing groups in brackets, such as (CH₃)

This method helps visualize complex molecules simply by translating the IUPAC names into structured formulae, illustrating their exact atomic placements efficiently.

Carbon Chains

Carbon chains are the backbone of organic molecules, forming the structural foundation. Length and connectivity of carbon chains determine the properties and classification of the compound.
In the context of IUPAC nomenclature, the longest continuous carbon chain is identified as the parent structure. For example, in the compound 3-ethylheptane, the main chain is heptane, consisting of seven carbon atoms. The parent chain decides the root name, and branches or substituents stem from it.

Secondary carbon chains or branches add diversity, influencing the compound's chemical and physical properties. Understanding the arrangement of carbon chains and how various substituents attach to them is critical in drawing accurate structural diagrams. This conceptualization aids in both theoretical studies and practical applications such as synthesis, analysis, and predicting reactivity patterns of organic substances.