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Ch.21 - Organic Chemistry
Chapter 21, Problem 43a,c

Draw a structure for each alkane. a. 3-ethylhexane c. 2,3-dimethylbutane

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1
Identify the parent chain: The parent chain is the longest continuous chain of carbon atoms. In this case, it is 'hexane', which means the parent chain has 6 carbon atoms.
Number the carbon atoms in the parent chain: Start numbering from the end closest to the substituent to give the substituent the lowest possible number. For hexane, number the carbon atoms from 1 to 6.
Identify and place the substituent: The substituent is '3-ethyl', which means there is an ethyl group (C2H5) attached to the third carbon of the hexane chain.
Draw the carbon skeleton: Draw a straight chain of 6 carbon atoms for hexane. Then, attach the ethyl group to the third carbon atom.
Add hydrogen atoms: Complete the structure by adding hydrogen atoms to each carbon atom, ensuring that each carbon forms four bonds in total.

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Key Concepts

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

Alkanes

Alkanes are saturated hydrocarbons consisting only of carbon (C) and hydrogen (H) atoms, connected by single bonds. They follow the general formula CnH2n+2, where 'n' is the number of carbon atoms. Alkanes are characterized by their relatively low reactivity and are commonly found in natural gas and petroleum.
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Structural Isomers

Structural isomers are compounds that have the same molecular formula but differ in the arrangement of atoms. In the case of alkanes, this means that different structural forms can exist for the same number of carbon atoms, leading to variations in physical and chemical properties. Understanding structural isomers is crucial for drawing accurate chemical structures.
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IUPAC Nomenclature

IUPAC nomenclature is a systematic method for naming chemical compounds, ensuring that each compound has a unique and descriptive name. For alkanes, the name reflects the longest continuous carbon chain and any substituents. In the case of 3-ethylhexane, the name indicates a hexane chain with an ethyl group attached to the third carbon, guiding the drawing of its structure.
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