Textbook Question
Given the molecular formula, calculate the index of hydrogen deficiency.
(b) C4H9ON
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1. A Review of General Chemistry
Degrees of Unsaturation
Problem 7e
Textbook Question
What is the index of hydrogen deficiency for each of the following molecular formulas?
(e) C6H12O2
Verified step by step guidance1
Step 1: Understand the concept of the Index of Hydrogen Deficiency (IHD). The IHD, also known as the degree of unsaturation, indicates the number of rings, double bonds, or triple bonds in a molecule. It is calculated using the formula: IHD = (2C + 2 - H + N - X) / 2, where C = number of carbons, H = number of hydrogens, N = number of nitrogens, and X = number of halogens.
Step 2: Identify the molecular formula components. For the given formula C₆H₁₂O₂, we have C = 6, H = 12, and O = 2. Note that oxygen atoms (O) do not affect the IHD calculation, so they can be ignored in this context.
Step 3: Substitute the values into the IHD formula. Using the formula IHD = (2C + 2 - H) / 2, substitute C = 6 and H = 12. The formula becomes: IHD = (2(6) + 2 - 12) / 2.
Step 4: Simplify the expression. Perform the arithmetic operations in the numerator: 2(6) = 12, then add 2 to get 14, and subtract 12 to get 2. Divide the result by 2 to calculate the IHD.
Step 5: Interpret the result. The IHD value represents the total number of rings and/or multiple bonds in the molecule. Use this information to analyze the structure of the compound.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Index of Hydrogen Deficiency (IHD)
The Index of Hydrogen Deficiency (IHD) is a measure used in organic chemistry to determine the degree of unsaturation in a molecular formula. It indicates the number of rings and/or multiple bonds present in a compound. Each double bond or ring contributes one to the IHD, while each triple bond contributes two. The formula for calculating IHD is IHD = (2C + 2 + N - H - X) / 2, where C is the number of carbons, N is the number of nitrogens, H is the number of hydrogens, and X is the number of halogens.
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Molecular Formula Interpretation
A molecular formula provides the number of each type of atom in a compound but does not indicate the structure. For example, C₆H₁₂O₂ indicates there are six carbon atoms, twelve hydrogen atoms, and two oxygen atoms. Understanding how to interpret this formula is crucial for calculating the IHD, as it allows you to identify the elements involved and their contributions to the overall saturation of the molecule.
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Unsaturation in Organic Compounds
Unsaturation refers to the presence of double or triple bonds in organic compounds, which affects their reactivity and physical properties. Compounds with higher unsaturation typically have lower hydrogen counts relative to their carbon counts. Recognizing unsaturation is essential for predicting the behavior of organic molecules, as it influences reactions such as addition and elimination, and is directly related to the calculation of the IHD.
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