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Ch.1 - Structure and Bonding
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 1, Problem 36

Some of the following molecular formulas correspond to stable compounds. When possible, draw a stable structure for each formula. Propose a general rule for the numbers of hydrogen atoms in stable hydrocarbons.

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1
Identify the general formula for alkanes, which is CnH2n+2. This formula represents saturated hydrocarbons where all carbon atoms are connected by single bonds.
For each molecular formula, determine if it fits the alkane formula. For example, CH4 fits the formula CnH2n+2 with n=1, making it a stable alkane (methane).
Identify the general formula for alkenes, which is CnH2n. This formula represents unsaturated hydrocarbons with at least one carbon-carbon double bond.
For each molecular formula, determine if it fits the alkene formula. For example, C2H4 fits the formula CnH2n with n=2, making it a stable alkene (ethylene).
Propose a general rule: In stable hydrocarbons, the number of hydrogen atoms is determined by the type of hydrocarbon. Alkanes follow CnH2n+2, alkenes follow CnH2n, and alkynes follow CnH2n-2.

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Key Concepts

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

Hydrocarbons

Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon atoms. They can be classified into aliphatic (straight or branched chains) and aromatic (ring structures) hydrocarbons. Understanding the structure and types of hydrocarbons is essential for predicting their stability and reactivity.
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Degree of Unsaturation

The degree of unsaturation indicates the number of rings and multiple bonds in a hydrocarbon. Each double bond or ring reduces the number of hydrogen atoms that can be attached to the carbon skeleton. This concept helps in determining the stability of a compound and is crucial for drawing accurate molecular structures.
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The difference between saturated and unsaturated molecules.

General Formula for Alkanes

The general formula for alkanes, which are saturated hydrocarbons, is CnH2n+2, where 'n' is the number of carbon atoms. This formula illustrates the relationship between the number of carbon and hydrogen atoms in stable alkanes, guiding the drawing of structures and understanding the composition of various hydrocarbons.
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Functionalizing Alkanes