Textbook Question
Calculate the index of hydrogen deficiency for the following molecular formulas and structures.
(f) C6H8O2
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1. A Review of General Chemistry
Degrees of Unsaturation
Problem 48c
Textbook Question
For each molecular formula, represent all constitutional isomers using line-angle drawings.
(c) C4H10
Verified step by step guidance1
Understand the problem: The molecular formula C₄H₁₀ represents an alkane (a saturated hydrocarbon with only single bonds). Constitutional isomers are compounds with the same molecular formula but different connectivity of atoms. We need to draw all possible unique structures for C₄H₁₀ using line-angle drawings.
Step 1: Start with the simplest structure, a straight-chain alkane. For C₄H₁₀, this is butane. Draw a four-carbon chain with single bonds between the carbons. Add hydrogens to each carbon to satisfy the octet rule (each carbon should have four bonds).
Step 2: Consider branching to create isomers. Remove one carbon from the main chain and attach it as a branch to another carbon. For C₄H₁₀, this results in a three-carbon chain with a single methyl group (-CH₃) attached to the central carbon. This structure is called isobutane (or 2-methylpropane).
Step 3: Verify that all possible isomers have been drawn. For C₄H₁₀, there are only two constitutional isomers: butane and isobutane. Ensure that no other unique connectivity exists for this molecular formula.
Step 4: Represent each isomer using line-angle drawings. For butane, draw a straight line with three vertices (representing the four carbons). For isobutane, draw a 'T' shape, where the central vertex represents the carbon with three bonds (one to the methyl group and two to other carbons).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Constitutional Isomers
Constitutional isomers are compounds that have the same molecular formula but differ in the connectivity of their atoms. This means that the arrangement of atoms in the molecule varies, leading to different structural forms. Understanding constitutional isomers is crucial for recognizing how variations in structure can affect the properties and reactivity of organic compounds.
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Line-Angle Drawings
Line-angle drawings, also known as skeletal structures, are a shorthand way of representing organic molecules. In these drawings, carbon atoms are represented by the ends and intersections of lines, while hydrogen atoms are typically omitted for clarity. This method simplifies the visualization of complex structures, making it easier to identify isomers and their connectivity.
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Molecular Formula
A molecular formula indicates the number and types of atoms in a molecule, represented by chemical symbols and subscripts. For example, C₄H₁₀ indicates a molecule with four carbon atoms and ten hydrogen atoms. The molecular formula is essential for determining possible isomers, as it provides the foundational information needed to explore different structural arrangements.
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