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Ch. 7 - Structure and Synthesis of Alkenes; Elimination
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh. 7 - Structure and Synthesis of Alkenes; EliminationProblem 2
Chapter 7, Problem 2

Determine the number of elements of unsaturation in the molecular formula C4H6. Give all nine possible structures having this formula. Remember that
a double bond = one element of unsaturation
a ring = one element of unsaturation
a triple bond = two elements of unsaturation

Verified step by step guidance
1
Step 1: Calculate the degree of unsaturation using the formula: Degree of Unsaturation = (2C + 2 + N - H) / 2, where C is the number of carbons, N is the number of nitrogens, and H is the number of hydrogens.
Step 2: Substitute the values from the molecular formula C4H9N into the formula: Degree of Unsaturation = (2(4) + 2 + 1 - 9) / 2.
Step 3: Simplify the expression to find the degree of unsaturation. This will tell you how many rings and/or multiple bonds are present in the molecule.
Step 4: Use the degree of unsaturation to determine possible structures. Consider combinations of rings, double bonds, and triple bonds that match the degree of unsaturation.
Step 5: Draw all possible structures that fit the molecular formula C4H9N and the calculated degree of unsaturation. Ensure that each structure adheres to the rules of valency for carbon and nitrogen.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Elements of Unsaturation

Elements of unsaturation, also known as degrees of unsaturation, indicate the number of rings and multiple bonds (double or triple) in a molecule. Each double bond or ring counts as one element of unsaturation, while a triple bond counts as two. This concept helps in determining the possible structures of a molecule from its molecular formula.
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Molecular Formula Analysis

Analyzing a molecular formula involves calculating the elements of unsaturation to predict possible structures. For a given formula, the degrees of unsaturation can be calculated using the formula: (2C + 2 + N - H)/2, where C, N, and H are the number of carbon, nitrogen, and hydrogen atoms, respectively. This calculation helps in identifying the presence of rings or multiple bonds.
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Structural Isomerism

Structural isomerism occurs when molecules with the same molecular formula have different connectivity of atoms. In the context of C4H9N, structural isomers can include variations in the arrangement of carbon chains, the position of nitrogen, and the presence of rings or multiple bonds. Understanding isomerism is crucial for enumerating all possible structures for a given formula.
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Related Practice
Textbook Question

Give five examples of structures with this formula (C6H12). At least one should contain a ring, and at least one should contain a double bond.

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

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Textbook Question

If a hydrocarbon has nine carbon atoms, three double bonds, and one ring, how many hydrogen atoms must it have?

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

3
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Textbook Question

For each of the following molecular formulas, determine the number of elements of unsaturation, and draw three examples. 

d. C5H5NO2

e. C6H3NClBr 

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Textbook Question

Calculate the number of elements of unsaturation implied by the molecular ­formula C6H12.

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

1
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Textbook Question

For each of the following molecular formulas, determine the number of elements of unsaturation, and draw three examples.

a. C4H4Cl2

b. C4H8O

c. C6H8O2

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Textbook Question

Draw five more compounds of formula C4H6NOCl.

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