The molecular formula of propanone is CH3COCH3 and the molecular formula of propyne is CH3CCH

The molecular formula of propanone is CH3COCH3 and the molecular formula of propyne is CH3CCH.

(i) Determine the number of atoms in the propanone structure that are sp3 hybridized.

(ii) Determine the number of atoms in the propanone structure that are sp2 hybridized.

(iii) Predict the approximate carbon to carbon to carbon bond angle in propanone.

(i) Determine the total number of pi and sigma bonds in the propyne molecule. pi bonds sigma bonds

(ii) Predict the approximate carbon to carbon to carbon bond angle in propyne. °

(iii) Indicate the hybridization of carbon found in the propyne molecule. Select all that apply. sp2 sp sp3 dsp3 d2sp3

The correct answer and explanation is :

Let’s break this down step by step:

Propanone (CH₃COCH₃):

1. (i) Number of atoms in propanone that are sp³ hybridized:

• In the molecular structure of propanone, there are three carbon atoms and each carbon atom in the two methyl (CH₃) groups is sp³ hybridized.
• Additionally, the two hydrogen atoms attached to each methyl carbon are also sp³ hybridized.
• The carbon atom of the carbonyl group (C=O) is not sp³ hybridized (it’s sp² hybridized).
• Answer: There are 6 atoms that are sp³ hybridized: 2 carbons from CH₃ groups and 4 hydrogens.

1. (ii) Number of atoms in propanone that are sp² hybridized:

• The carbonyl carbon (C=O) is sp² hybridized because it is double-bonded to an oxygen atom and forms one sigma bond and one pi bond.
• The oxygen atom in the carbonyl group is also sp² hybridized because it forms a sigma bond with the carbonyl carbon and has lone pairs in sp² orbitals.
• Answer: There are 2 atoms that are sp² hybridized: 1 carbon from the carbonyl group and 1 oxygen from the carbonyl group.

1. (iii) Carbon-carbon-carbon bond angle in propanone:

• The carbonyl carbon (C=O) is sp² hybridized, so the bond angles around it are approximately 120°, which is typical for sp² hybridization.
• The methyl groups (CH₃) are sp³ hybridized, and the bond angles around them are approximately 109.5°.
• However, the overall bond angle around the central carbon (which connects the two CH₃ groups and the carbonyl group) will likely be closer to 120°, as the carbonyl group dominates due to its sp² hybridization.
• Answer: The approximate carbon-carbon-carbon bond angle in propanone is 120°.

Propyne (CH₃C≡CH):

1. (i) Number of pi and sigma bonds in propyne:

• In propyne, the carbon-carbon triple bond consists of 1 sigma bond and 2 pi bonds.
• The C-H bonds are sigma bonds, and there are 4 C-H bonds in total.
• The C-C bond between the two carbons is 1 sigma and 2 pi bonds, and the other C-H bonds are 4 sigma bonds.
• Answer: In propyne, there are 1 sigma bond and 2 pi bonds in the C≡C triple bond, and 4 sigma bonds in the C-H bonds.

1. (ii) Carbon-carbon-carbon bond angle in propyne:

• In propyne, the central carbon atom is sp hybridized (due to the triple bond), and the angle between the bonds will be approximately 180°, consistent with the linear geometry of sp hybridization.
• Answer: The approximate bond angle in propyne is 180°.

1. (iii) Hybridization of carbon atoms in propyne:

• The central carbon (C≡C) in propyne is sp hybridized because it forms a triple bond (one sigma and two pi bonds) with the other carbon.
• The two terminal carbons, each bonded to one hydrogen atom and one carbon atom (C-H and C-C), are also sp hybridized because each is involved in a triple bond (sigma and pi bonds).
• Answer: The hybridization of the carbon atoms in propyne is sp for all three carbon atoms.

Summary:

• Propanone:
• sp³ hybridized atoms: 6 (2 carbons from CH₃ groups and 4 hydrogens).
• sp² hybridized atoms: 2 (1 carbon from the carbonyl group and 1 oxygen).
• Approximate bond angle: 120°.
• Propyne:
• Pi and sigma bonds: 1 sigma bond and 2 pi bonds in the C≡C bond, 4 sigma bonds in the C-H bonds.
• Approximate bond angle: 180°.
• Hybridization of carbon atoms: All carbon atoms are sp hybridized.