Many primary amines, RNH \(_{2},\) where \(R\) is a carbon-containing fragment such as \(C H_{3}, C H_{3} C H_{2},\) 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 \(^{4} \mathrm{R}^{\prime \prime}\) . (b) What kind of reactant with a primary amine can produce a tetrahedral intermediate?

To draw a hybrid orbital picture of a primary amine with a simple carbon atom as the carbon-containing fragment, let's start by understanding the electronic configuration of the nitrogen atom. Nitrogen has 5 valence electrons, with an electronic configuration of \(1s^{2}2s^{2}2p^{3}\). When nitrogen forms a primary amine, it uses one of its 2s electrons and three 2p electrons to create four hybrid orbitals, typically referred to as sp^3 hybridization. These hybrid orbitals form a tetrahedron with angles of approximately 109.5 degrees between them. These sp^3 hybrid orbitals will be involved in forming bonds with the R group (carbon-containing fragment) and two hydrogen atoms. To draw this hybrid orbital picture: 1. Draw a nitrogen atom surrounded by 4 hybrid orbitals (sp^3), pointing towards the corners of a tetrahedron. 2. Draw the R group attached to one of the hybrid orbitals. 3. Draw two hydrogen atoms, each attached to another hybrid orbital. 4. Show the unshared electron pair of the nitrogen atom in the remaining hybrid orbital.

In order to produce a tetrahedral intermediate in a reaction with a primary amine (RNH2), we need a reactant that is electron-deficient, which can accept an electron pair from the nitrogen atom of the primary amine. Such a reactant will engage with the nitrogen atom and share an electron pair, forming a new bond. A common type of reactant that can produce a tetrahedral intermediate with a primary amine is an electrophile, such as a carbonyl compound (R'CO). Here's how the reaction takes place: 1. The nitrogen atom in the primary amine RNH2 acts as a nucleophile, donating its electron pair to the electron-deficient carbonyl carbon (C=O) in the reactant R'CO. 2. The carbonyl bond (C=O) breaks, and one of the carbonyl bond electrons shift towards the oxygen atom, creating a tetrahedral intermediate. The oxygen atom is now negatively charged, while the nitrogen atom still retains a positive charge due to its shared electron pair with the carbonyl carbon. Therefore, a reactant that can produce a tetrahedral intermediate with a primary amine is an electrophilic carbonyl compound (R'CO).