Two isomers share the molecular formula C3H4

Two isomers share the molecular formula C3H4. In Structure A two of the carbon atoms are sp hybridized and one carbon atom is sp3 hybridized. In Structure B, two of the carbon atoms are sp2 hybridized and one carbon atom is sp hybridized. b)Draw “3D�-looking structures on paper, make a sketch of each of the isomers. (This should be a sketch of the molecules, not diagrams of overlapping orbitals!) Your drawing should show the correct molecular geometry around each carbon atom.
Two isomers share the molecular formula C3H4. In Structure A two of
the carbon atoms are sp hybridized and one carbon atom is sp3 hybridized. In Structure B, two of the carbon atoms are sp2 hybridized and one carbon atom is sp
hybridized.

b)Draw “3D�-looking structures on paper, make a sketch of each of the isomers. (This should be a sketch of the
molecules, not diagrams of overlapping orbitals!) Your drawing should show the
correct molecular geometry around each carbon atom. [HINT: NEITHER of these
molecules is planar!!! To draw them correctly, you will have to consider why!]

The Correct Answer and Explanation is :

The two isomers with the molecular formula C₃H₄ are likely to be propyne (C₃H₄) and allylidyne (C₃H₄). Let’s break down the explanation:

Isomer A: Propyne (CH≡C-CH₃)

In propyne, the structure involves a triple bond between two carbon atoms (C≡C) and a single bond with the third carbon (CH₃). This molecule has:

• Two sp-hybridized carbon atoms: The carbons involved in the triple bond (C≡C). The sp hybridization results in a linear geometry around these carbons (180° bond angles).
• One sp³-hybridized carbon atom: The carbon atom attached to the methyl group (CH₃). This carbon forms single bonds with hydrogen atoms and has a tetrahedral geometry (109.5° bond angles).
• This structure is not planar because the triple bond forces the molecule to bend at the CH₃ group, creating a non-planar geometry for the entire molecule.

Isomer B: Allylidyne (C₃H₄)

In allylidyne, the structure has a different arrangement with a triple bond between one carbon and the terminal carbon, and a double bond between the middle carbon and the terminal carbon. The molecular geometry includes:

• Two sp²-hybridized carbon atoms: The carbon atoms involved in the double bond (C=C). These carbons adopt a trigonal planar geometry with 120° bond angles.
• One sp-hybridized carbon atom: The carbon involved in the triple bond. It adopts a linear geometry with 180° bond angles.
• Similar to propyne, this molecule is also non-planar due to the nature of the bonds and the requirement for optimal spatial arrangement of atoms to minimize repulsions.

Sketch of Structures

1. Propyne: The structure looks like this:

• H₃C-≡C-H, with a tetrahedral carbon (sp³) at the CH₃ group and two sp-hybridized carbons in a linear arrangement.

1. Allylidyne: The structure looks like this:

• H₂C≡C-H, with a trigonal planar carbon (sp²) at the C=C bond and a linear geometry at the sp-hybridized carbon involved in the triple bond.

Why the Structures are Non-Planar

Neither molecule is planar due to the geometries of the hybridized carbons. In propyne, the tetrahedral carbon at the CH₃ group prevents the molecule from being flat. In allylidyne, the sp² carbons cause the molecule to bend at the sp-hybridized carbon, preventing a planar structure.