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Ch.1 - Structure and Bonding
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.1 - Structure and BondingProblem 59a,b
Chapter 1, Problem 59a,b

Give the relationships between the following pairs of structures. The possible relationships are as follows: same ­compound, cis-trans isomers, constitutional (structural) isomers, and not isomers (different molecular formula).
(a) CH3CH2CH2CH3 and (CH3)3CH
(b) CH2=CH–CH2Cl and CHCl=CH–CH3

Verified step by step guidance
1
Step 1: Analyze the molecular formula of each compound in pair (a). CH3CH2CH2CH3 is a straight-chain alkane with the molecular formula C4H10, while (CH3)3CH is a branched alkane with the same molecular formula C4H10.
Step 2: Determine the relationship between the compounds in pair (a). Since both compounds have the same molecular formula but differ in connectivity (straight-chain vs branched), they are constitutional (structural) isomers.
Step 3: Analyze the molecular formula of each compound in pair (b). CH2=CHCH2Cl has the molecular formula C3H5Cl, while CHCl=CHCH3 has the molecular formula C3H5Cl as well.
Step 4: Examine the connectivity and arrangement of atoms in pair (b). CH2=CHCH2Cl has a chlorine atom attached to the terminal carbon of the propene chain, while CHCl=CHCH3 has the chlorine atom attached to the middle carbon of the propene chain. This difference in connectivity indicates that they are constitutional (structural) isomers.
Step 5: Summarize the relationships: Pair (a) consists of constitutional isomers due to different connectivity of atoms in the same molecular formula. Pair (b) also consists of constitutional isomers due to different connectivity of atoms in the same molecular formula.

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Key Concepts

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

Isomerism

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations. This can lead to different physical and chemical properties. The main types of isomers include structural isomers, which differ in the connectivity of atoms, and stereoisomers, which have the same connectivity but differ in the spatial arrangement of atoms.
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Cis-Trans Isomerism

Cis-trans isomerism is a type of stereoisomerism that occurs in compounds with restricted rotation around a double bond or a ring structure. In cis isomers, substituents are on the same side of the double bond or ring, while in trans isomers, they are on opposite sides. This difference in arrangement can significantly affect the physical properties of the compounds, such as boiling points and solubility.
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Constitutional Isomers

Constitutional isomers, also known as structural isomers, are compounds that have the same molecular formula but differ in the connectivity of their atoms. This means that the atoms are bonded together in different ways, leading to distinct compounds with unique properties. Understanding constitutional isomers is crucial for identifying relationships between different chemical structures and predicting their reactivity.
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Related Practice
Textbook Question

Dimethyl sulfoxide (DMSO) has been used as an anti-inflammatory rub for race horses. DMSO and acetone appear to have similar structures, but the C=O carbon atom in acetone is planar, while the S=O sulfur atom in DMSO is ­pyramidal. Draw Lewis structures for DMSO and acetone, predict the hybridizations, and explain these observations.

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Textbook Question

Which of the following compounds show cis-trans isomerism? Draw the cis and trans isomers of the ones that do.

(d)

(e)

(f) CH3CH=NCH3

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Textbook Question

Give the relationships between the following pairs of structures. The possible relationships are as follows: same ­compound, cis-trans isomers, constitutional (structural) isomers, and not isomers (different molecular formula).

(c)

(d)

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Textbook Question

Which of the following compounds show cis-trans isomerism? Draw the cis and trans isomers of the ones that do.

(a) CH3CH=CHCH3

(b) CH3C≡CCH3

(c) CH2=C(CH3)2

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Textbook Question

In pent-2-yne (CH3CCCH2CH3), there are four atoms in a straight line. Use dashed lines and wedges to draw a three-dimensional representation of this molecule, and circle the four atoms that are in a straight line.

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