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Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
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All textbooksMullins 1st EditionCh. 3 - Alkanes and Cycloalkanes: Properties and Conformational AnalysisProblem 6c
Chapter 2, Problem 6c

How many hydrogens would you expect a 24-carbon compound from each of the following molecular classes to have?
(c) Alkyne

Verified step by step guidance
1
Step 1: Recall the general formula for alkynes. Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond. The general formula for an alkyne is CₙH₂ₙ₋₂, where 'n' is the number of carbon atoms.
Step 2: Identify the number of carbon atoms in the compound. In this case, the compound has 24 carbon atoms, so n = 24.
Step 3: Substitute the value of 'n' into the general formula for alkynes. The formula becomes H = 2(24) - 2.
Step 4: Simplify the expression to determine the number of hydrogen atoms. Perform the arithmetic operation to calculate the total hydrogens.
Step 5: Verify the result by ensuring it aligns with the molecular structure of an alkyne, which must have at least one triple bond and follow the CₙH₂ₙ₋₂ formula.

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Key Concepts

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

Hydrocarbon Structure

Hydrocarbons are organic compounds consisting solely of carbon and hydrogen. The structure of hydrocarbons can vary significantly, leading to different classes such as alkanes, alkenes, and alkynes. Understanding the basic structure helps in predicting the number of hydrogen atoms based on the type of hydrocarbon.
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Aromaticity of Hydrocarbons

Alkynes

Alkynes are a class of hydrocarbons characterized by at least one carbon-carbon triple bond. The general formula for alkynes is CnH2n-2, where 'n' is the number of carbon atoms. This formula indicates that alkynes have fewer hydrogen atoms compared to alkanes and alkenes due to the presence of the triple bond.
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Alkyne Hydration

Degree of Unsaturation

The degree of unsaturation refers to the total number of rings and multiple bonds in a compound. Each triple bond contributes two degrees of unsaturation, which reduces the number of hydrogen atoms in the molecule. For alkynes, this concept is crucial for calculating the expected number of hydrogen atoms based on the number of carbon atoms.
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The difference between saturated and unsaturated molecules.
Related Practice
Textbook Question

Choose the molecule in each pair you'd expect to have the higher boiling point. Explain your reasoning.

(a) eicosane ( C20H42) vs pentadecane

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Textbook Question

How many hydrogens would you expect a 24-carbon compound from each of the following molecular classes to have?

(a) Alkane

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Textbook Question

Choose the molecule in each pair you'd expect to have the higher boiling point. Explain your reasoning.

(b)

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Textbook Question

What is the hybridization of carbon in each of the following molecules?

(d)

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Textbook Question

How many hydrogens would you expect a 24-carbon compound from each of the following molecular classes to have?

(b) Alkene

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Textbook Question

Draw the molecular orbital picture for propane. Your picture should clearly show the shape and hybridization of the carbons. Label all σ bonds.

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