Final answer:
The C-H stretch in a sp² hybridized carbon is found in the IR spectrum typically between 3000 and 3150 cm-1, indicative of slightly polar C-H bonds in a trigonal planar geometry with a partial positive charge on the hydrogen atoms.
Step-by-step explanation:
The C-H stretching vibration of a sp² hybridized carbon can be observed in the infrared (IR) spectrum typically between 3000 and 3150 cm-1. This stretch is due to the sp² hybridized carbon atoms forming a trigonal planar geometry, with three σ-bonds using sp² hybrid orbitals and one π-bond using the unhybridized p orbital. The C-H bond in this configuration is slightly polar with a partial positive (δ+) charge on the hydrogen atom.
In a molecule like ethene (H₂C=CH₂), the electrostatic potential map shows a concentration of electron density around the C=C double bond, which is due to the pi-bonding electrons placed above and below the sigma bond. The hydrogen atoms attached to the sp² hybridized carbon display a bluish color in the electrostatic potential map, indicating the slightly polar nature of the C-H bond. The exact position of the C-H stretching vibration in the IR spectrum can vary slightly depending on the molecules' specific substituents and molecular structure.