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Ch.1 - Structure and Bonding
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 1, Problem 17a

Predict the hybridization, geometry, and bond angles for the central atoms in
a. but-2-ene, CH3CH=CHCH3

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1
Identify the central atoms in but-2-ene. The central atoms are the two carbon atoms involved in the double bond, which are the second and third carbon atoms in the chain.
Determine the hybridization of the central carbon atoms. In but-2-ene, the carbon atoms involved in the double bond are sp² hybridized. This is because each carbon forms three sigma bonds and has one pi bond.
Predict the geometry around the sp² hybridized carbon atoms. The geometry is trigonal planar, which is typical for sp² hybridized atoms.
Estimate the bond angles around the sp² hybridized carbon atoms. In a trigonal planar geometry, the bond angles are approximately 120 degrees.
Consider the overall structure of but-2-ene. The molecule is planar around the double bond, and the geometry and bond angles are consistent with the sp² hybridization of the central carbon atoms.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hybridization

Hybridization is the process of mixing atomic orbitals to form new hybrid orbitals, which can form sigma bonds or accommodate lone pairs. In but-2-ene, the central carbon atoms involved in the double bond are sp2 hybridized, meaning one s orbital and two p orbitals combine to form three equivalent sp2 orbitals, allowing for a planar structure with 120-degree bond angles.
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Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms around a central atom. For sp2 hybridized atoms, as in the case of the central carbons in but-2-ene, the geometry is trigonal planar. This means the atoms bonded to the central carbon lie in a single plane, forming a triangular shape with 120-degree angles between them.
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Bond Angles

Bond angles are the angles between adjacent bonds at an atom. In but-2-ene, the sp2 hybridization of the central carbon atoms results in bond angles of approximately 120 degrees. This is characteristic of a trigonal planar geometry, where the electron pairs are evenly distributed around the central atom to minimize repulsion, according to VSEPR theory.
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