Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook

Bruice 8th Edition

Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure

Problem 61

Chapter 4, Problem 61

Draw a skeletal structure for an alkane that has
a. six carbons, all secondary.
b. eight carbons and only primary hydrogens.
c. seven carbons with two isopropyl groups.

Verified step by step guidance

Identify the general formula for alkanes, which is C_nH_{2n+2}, and understand that alkanes are saturated hydrocarbons with only single bonds.

For part (a), recognize that a secondary carbon is bonded to two other carbons. To have six carbons all secondary, consider a cyclic structure like cyclohexane, where each carbon is bonded to two other carbons.

For part (b), understand that primary hydrogens are attached to primary carbons, which are bonded to only one other carbon. To have eight carbons with only primary hydrogens, consider a linear structure like n-octane, where the terminal carbons are primary.

For part (c), recall that an isopropyl group is a branched alkyl group with the structure (CH_3)_2CH-. To have seven carbons with two isopropyl groups, consider a structure like 2,3-dimethylpentane, where the main chain is five carbons long and two isopropyl groups are attached.

Draw the skeletal structures based on the descriptions: (a) cyclohexane for six secondary carbons, (b) n-octane for eight carbons with primary hydrogens, and (c) 2,3-dimethylpentane for seven carbons with two isopropyl groups.

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Key Concepts

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

Alkane Structure

Alkanes are saturated hydrocarbons consisting only of carbon (C) and hydrogen (H) atoms, connected by single bonds. The general formula for alkanes is CnH2n+2, where 'n' is the number of carbon atoms. Understanding the skeletal structure of alkanes is crucial, as it visually represents the arrangement of carbon atoms and their associated hydrogen atoms, which is essential for identifying the type of alkane being described.

Secondary and Primary Carbons

In organic chemistry, carbon atoms can be classified based on the number of other carbon atoms they are bonded to. A secondary carbon is bonded to two other carbons, while a primary carbon is bonded to only one. This classification is important for constructing the skeletal structures requested in the question, as it determines the connectivity and branching of the carbon chain in the alkane.

Isopropyl Groups

An isopropyl group is a branched alkyl group derived from propane, consisting of three carbon atoms with the structure -C(CH3)2. When constructing skeletal structures, recognizing how to represent isopropyl groups is essential, especially when multiple groups are present, as in the case of the seven-carbon alkane with two isopropyl groups. This understanding aids in accurately depicting the molecular structure and ensuring correct connectivity.

Draw a skeletal structure for an alkane that hasa. six carbons, all secondary.b. eight carbons and only primary hydrogens.c. seven carbons with two isopropyl groups.