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Ch.14 - Chemical Kinetics
All textbooksBrown 14th EditionCh.14 - Chemical KineticsProblem 123
Chapter 14, Problem 123

Many primary amines, RNH2, where R is a carbon-containing fragment such as CH3, CH3CH2, and so on, undergo reactions where the transition state is tetrahedral. (b) What kind of reactant with a primary amine can produce a tetrahedral intermediate?

Verified step by step guidance
1
Understand the concept of a tetrahedral intermediate: In organic chemistry, a tetrahedral intermediate is a transient structure formed during certain reactions, characterized by a central atom bonded to four other atoms or groups, creating a tetrahedral geometry.
Identify the type of reaction that involves a tetrahedral intermediate: A common reaction involving primary amines that leads to a tetrahedral intermediate is nucleophilic addition. This typically occurs when a nucleophile, such as a primary amine, attacks a carbonyl group.
Recognize the structure of a carbonyl group: A carbonyl group consists of a carbon atom double-bonded to an oxygen atom (C=O). This group is highly reactive due to the polarity of the C=O bond, making it susceptible to nucleophilic attack.
Determine the reactant that can form a tetrahedral intermediate with a primary amine: The primary amine can react with a carbonyl compound, such as an aldehyde or ketone, to form a tetrahedral intermediate. The nucleophilic nitrogen atom of the amine attacks the electrophilic carbon atom of the carbonyl group.
Visualize the formation of the tetrahedral intermediate: When the primary amine attacks the carbonyl carbon, the double bond between carbon and oxygen is temporarily broken, and the carbon atom forms new single bonds with the nitrogen atom of the amine and the oxygen atom, resulting in a tetrahedral geometry.

Key Concepts

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

Primary Amines

Primary amines are organic compounds characterized by the presence of one amino group (-NH2) attached to a carbon atom. The carbon atom can be part of a larger hydrocarbon chain or ring, represented as 'R' in the general formula RNH2. These compounds are known for their nucleophilic properties, allowing them to react with electrophiles in various chemical reactions.
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Rules for Naming Amines

Tetrahedral Intermediate

A tetrahedral intermediate is a transient species that forms during certain chemical reactions, particularly those involving nucleophilic substitution or addition. In this structure, a central atom, typically carbon, is bonded to four substituents, resulting in a tetrahedral geometry. This intermediate is crucial in understanding the mechanism of reactions involving primary amines, as it indicates a change in hybridization and bonding during the reaction process.
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The crystal field splitting pattern for tetrahedral complexes has the d orbitals in between the axes as having the higher energy.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile, which is a species that donates an electron pair. In the context of primary amines, these reactions often lead to the formation of tetrahedral intermediates when the amine acts as a nucleophile, attacking an electrophilic carbon atom. Understanding this mechanism is essential for predicting the products and pathways of reactions involving primary amines.
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Related Practice
Textbook Question

The mechanism for the oxidation of HBr by O2 to form 2 H2O and Br2 is shown in Exercise 14.74. (c) Draw a plausible Lewis structure for the intermediate HOOBr. To what familiar compound of hydrogen and oxygen does it appear similar?

Textbook Question

The rates of many atmospheric reactions are accelerated by the absorption of light by one of the reactants. For example, consider the reaction between methane and chlorine to produce methyl chloride and hydrogen chloride:

Reaction 1: CH4(g) + Cl2(g) → CH3Cl(g) + HCl(g)

This reaction is very slow in the absence of light. However, Cl2(g) can absorb light to form Cl atoms:

Reaction 2: Cl2(g) + hv → 2 Cl(g)

Once the Cl atoms are generated, they can catalyze the reaction of CH4 and Cl2, according to the following proposed mechanism:

Reaction 3: CH4(g) + Cl(g) → CH3(g) + HCl(g)

Reaction 4: CH3(g) + Cl2(g) → CH3Cl(g) + Cl(g)

The enthalpy changes and activation energies for these two reactions are tabulated as follows:

Reaction ΔH° (kJ/mol) Ea (kJ/mol)

3 +4 17

4 -109 4 

(b) By using the data tabulated here, sketch a quantitative energy profile for the catalyzed reaction represented by reactions 3 and 4.

Textbook Question

Many primary amines, RNH2, where R is a carboncontaining fragment such as CH3, CH3CH2, and so on, undergo reactions where the transition state is tetrahedral. (a) Draw a hybrid orbital picture to visualize the bonding at the nitrogen in a primary amine (just use a C atom for 'R').