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Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 17 - Carbonyl Addition Reactions: Aldehydes and KetonesProblem 11
Chapter 16, Problem 11

Identify the bonds broken and formed in the following addition reaction.
(a) Would you expect this reaction to be favored based on entropy?
(b) Based on enthalpy [qualitatively]?
(c) Overall?
Chemical reaction showing the formation of an imine from an aldehyde and an amine, with bonds broken and formed indicated.

Verified step by step guidance
1
Identify the bonds broken: In the given reaction, the carbonyl group (C=O) in the cyclohexanone is broken. The pi bond of the carbonyl group is broken as the nucleophilic amine attacks the carbonyl carbon.
Identify the bonds formed: A new C-N bond is formed between the carbonyl carbon and the nitrogen of the amine. Additionally, an O-H bond is formed as the oxygen of the carbonyl group gains a hydrogen atom.
Entropy consideration: The reaction involves two reactant molecules combining to form a single product molecule. Generally, reactions that result in a decrease in the number of molecules are not favored by entropy, as entropy tends to favor an increase in disorder.
Enthalpy consideration: Qualitatively, the formation of new bonds (C-N and O-H) can release energy, making the reaction exothermic. Breaking the C=O pi bond requires energy, but the formation of stronger sigma bonds (C-N and O-H) can compensate for this, potentially making the reaction enthalpically favorable.
Overall consideration: The reaction may be favored overall if the enthalpic gain from forming new bonds outweighs the entropic loss from the decrease in the number of molecules. The reaction's favorability will depend on the balance between these enthalpic and entropic factors.

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Key Concepts

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

Addition Reactions

Addition reactions involve the breaking of π bonds (typically in alkenes or alkynes) and the formation of new σ bonds with reactants. In these reactions, two reactants combine to form a single product, which often leads to an increase in the number of bonds formed, impacting the overall stability and energy of the system.
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Entropy

Entropy is a measure of disorder or randomness in a system. In the context of chemical reactions, an increase in the number of gas molecules or a transition from a more ordered state to a less ordered state typically results in a positive change in entropy, favoring the reaction. Conversely, if a reaction leads to a decrease in the number of gas molecules, it may be less favored from an entropy perspective.
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Enthalpy

Enthalpy refers to the total heat content of a system and is a key factor in determining the favorability of a reaction. A reaction is generally favored if it results in a decrease in enthalpy (exothermic reaction), as this indicates that energy is released. Conversely, endothermic reactions, which absorb energy, may be less favorable unless compensated by a significant increase in entropy.
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Related Practice
Textbook Question

Predict the reagents or reactant(s) necessary to complete the following syntheses.

(b)

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Textbook Question

Another way the preceding might be presented is to say that the minor resonance structure(s) reveal the reactivity of a molecule. Show how the minor resonance structure(s) can help us understand that the following reactions occur with the regioselectivity shown.

(a)

(b)

(c)

790
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Textbook Question

Classify the following nucleophiles as strong, weak, or intermediate. Would you expect each to add to a carbonyl directly or wait for a carbocation to form?

(d)

1101
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Textbook Question

Predict the reagents or reactant(s) necessary to complete the following syntheses.

(c)

1186
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Textbook Question

Classify the following nucleophiles as strong, weak, or intermediate. Would you expect each to add to a carbonyl directly or wait for a carbocation to form?

b)

757
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Textbook Question

Classify the following nucleophiles as strong, weak, or intermediate. Would you expect each to add to a carbonyl directly or wait for a carbocation to form?

(a)

1154
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