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Chapter 4: Problem 55

Biacetyl and acetoin are added to margarine to make it taste more like butter. Complete the Lewis structures, predict values for all \(\mathrm{C}-\mathrm{C}-\mathrm{O}\) bond angles, and give the hybridization of the carbon atoms in these two compounds. Must the four carbon atoms and two oxygen atoms in biacetyl lie in the same plane? How many \(\sigma\) bonds and how many \(\pi\) bonds are there in biacetyl and acetoin?

Short Answer

Expert verified
The Lewis structures of biacetyl and acetoin are as follows: Biacetyl: \( \text{O}=\text{C}\text{-}\text{C}=\text{O} \) Acetoin: \( \text{O}=\text{C}\text{-}\text{C}\text{-}\text{O}\text{-}\text{H} \) The C-C-O bond angles are approximately 180° in biacetyl and 120° in acetoin. Both molecules have sp2-hybridized carbon atoms. In biacetyl, all four carbon atoms and two oxygen atoms lie in the same plane. Biacetyl has 5 σ bonds and 2 π bonds, while acetoin has 6 σ bonds and 1 π bond.

Step by step solution

01

(Draw Lewis structures of both molecules.)

Biacetyl has the molecular formula C4H6O2, and acetoin has the molecular formula C4H8O2. The Lewis structures for both molecules are as follows: Biacetyl: \( \text{O}=\text{C}\text{-}\text{C}=\text{O} \) Acetoin: \( \text{O}=\text{C}\text{-}\text{C}\text{-}\text{O}\text{-}\text{H} \) Step 2: Predict C-C-O bond angles
02

(Predict bond angles in biacetyl and acetoin.)

Both biacetyl and acetoin have C-C-O bond angles. In biacetyl, the carbon atoms are sp-hybridized, while in acetoin, the carbon atoms are sp2-hybridized. Therefore, the expected C-C-O bond angles are: Biacetyl: approximately 180° for both C-C-O angles (since the carbons are sp-hybridized) Acetoin: approximately 120° for the C-C-O angle (since the carbons are sp2-hybridized) Step 3: Determine hybridization of the carbon atoms
03

(Determine carbon atom hybridization for both molecules.)

To find the hybridization of the carbon atoms in both molecules, we count the number of electron domains around each carbon atom. In biacetyl, the central carbon atoms are both doubly bonded to oxygen atoms and singly bonded to each other. Thus, the central carbon atoms have three electron domains and are sp2-hybridized. In acetoin, the central carbon atoms both have a single bond to an oxygen and hydrogen atom, and a double bond to the other carbon atom, giving them three electron domains as well. Hence, they are also sp2-hybridized. Step 4: Determine if the four carbon atoms and two oxygen atoms in biacetyl lie in the same plane
04

(Checking the planarity of biacetyl's carbon and oxygen atoms.)

In biacetyl, the central carbon atoms are sp2-hybridized, which implies that the molecule has a trigonal planar geometry around these carbon atoms. Since oxygen atoms are also part of this trigonal planar geometry and all atoms are connected, all four carbon atoms and two oxygen atoms lie in the same plane in biacetyl. Step 5: Calculate the number of σ and π bonds present in both molecules
05

(Determine the number of σ and π bonds in both molecules.)

In biacetyl, there are three single bonds (C-C and two C-H) and two double bonds (both C=O). Each single bond is one σ bond and each double bond has one σ bond and one π bond. Therefore, biacetyl has 5 σ bonds and 2 π bonds. In acetoin, there are four single bonds (C-C, C-O-H, and two C-H) and one double bond (C=O). Each single bond is one σ bond and the double bond has one σ bond and one π bond. Therefore, acetoin has 6 σ bonds and 1 π bond.

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Most popular questions from this chapter

Determine the molecular structure and hybridization of the central atom \(X\) in the polyatomic ion \(X Y_{3}^{+}\) given the following information: A neutral atom of X contains 36 electrons, and the element Y makes an anion with a \(1-\) charge, which has the electron configuration \(1 s^{2} 2 s^{2} 2 p^{6}\).

Use the MO model to determine which of the following has the smallest ionization energy: \(\mathrm{N}_{2}, \mathrm{O}_{2}, \mathrm{N}_{2}^{2-}, \mathrm{N}_{2}^{-}, \mathrm{O}_{2}^{+} .\) Explain your answer.

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