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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 23b,c
Chapter 1, Problem 23b,c

Two compounds with the formula CH3–CH=N–CH3 are known.
b. What two compounds have this formula?
c. Explain why only one compound with the formula (CH3)2CNCH3 is known.

Verified step by step guidance
1
Step 1: Analyze the formula CH3CH=NCH3. This structure contains a double bond between the carbon and nitrogen atoms, which introduces the possibility of geometric isomerism (cis/trans or E/Z isomerism). This is because the groups attached to the double bond can have different spatial arrangements.
Step 2: Identify the two possible isomers for CH3CH=NCH3. In one isomer, the CH3 group attached to the carbon and the CH3 group attached to the nitrogen are on the same side of the double bond (cis or Z configuration). In the other isomer, these groups are on opposite sides of the double bond (trans or E configuration).
Step 3: Consider the formula (CH3)2CNCH3. This structure has a tertiary carbon atom bonded to the nitrogen atom. Due to the steric hindrance caused by the bulky (CH3)2C group, the nitrogen atom cannot form a double bond with the carbon atom. Instead, the nitrogen forms a single bond, resulting in only one possible compound with this formula.
Step 4: Explain why only one compound with the formula (CH3)2CNCH3 is known. The lack of a double bond between the carbon and nitrogen eliminates the possibility of geometric isomerism. Additionally, the steric hindrance from the bulky groups prevents alternative bonding arrangements.
Step 5: Summarize the findings. For CH3CH=NCH3, two isomers exist due to geometric isomerism (cis/trans or E/Z). For (CH3)2CNCH3, only one compound exists because steric hindrance and the absence of a double bond prevent isomerism.

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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 of atoms. In the case of CH3–CH=N–CH3, the compounds can exist as geometric isomers or structural isomers, leading to different chemical properties and reactivities.
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Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the context of the compounds with the formula CH3–CH=N–CH3, the presence of the imine functional group (C=N) plays a crucial role in determining the reactivity and stability of the compounds.
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Steric Hindrance

Steric hindrance occurs when the spatial arrangement of atoms within a molecule prevents certain reactions from occurring or makes them less favorable. In the case of (CH3)2CNCH3, the bulky methyl groups create steric hindrance around the nitrogen atom, limiting the formation of stable isomers and leading to the existence of only one compound.
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Related Practice
Textbook Question

Give the relationship between the following pairs of structures. The possible relationships are:

same compound

constitutional isomers (structural isomers)

cis-trans isomers

not isomers (different molecular formula)


(a)

(b)

(c)

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Textbook Question

Give the relationship between the following pairs of structures. The possible relationships are:

same compound

constitutional isomers (structural isomers)

cis-trans isomers

not isomers (different molecular formula)


(g) CH3–CH2–CH2–CH3 and CH3–CH=CH–CH3

(h) CH2=CH–CH2CH2CH3 and CH3–CH=CH–CH2CH3

(i) CH2=CHCH2CH2CH3 and CH3CH2CH2CH=CH2

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Textbook Question

For each pair of structures, determine whether they represent different compounds or a single compound.

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Textbook Question

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

(a) CHF=CHF

(b) F2C=CH2

(c) CH2=CH–CH2–CH3

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Textbook Question

Predict the hybridization, geometry, and bond angles for the carbon and nitrogen atoms in acetonitrile (CH3–C≡N:).

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Textbook Question

Predict the hybridization, geometry, and bond angles for the central atoms in

b. CH3CH=NH

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