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Ch.9 - Molecular Geometry and Bonding Theories
Chapter 9, Problem 61b

Consider the Lewis structure for glycine, the simplest amino acid:


(b) What are the hybridizations of the orbitals on the two oxygens and the nitrogen atom, and what are the approximate bond angles at the nitrogen?

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Identify the Lewis structure of glycine, focusing on the carboxyl group (COOH) and the amino group (NH2).
For the oxygen atoms in the carboxyl group, determine the hybridization by considering the number of sigma bonds and lone pairs. Typically, oxygen in a double bond (C=O) is sp2 hybridized, while oxygen in a single bond (O-H) is sp3 hybridized.
For the nitrogen atom in the amino group, consider the number of sigma bonds and lone pairs. Nitrogen with three sigma bonds and one lone pair is usually sp3 hybridized.
Estimate the bond angles around the nitrogen atom. In an sp3 hybridized nitrogen, the bond angles are approximately 109.5 degrees, but due to lone pair repulsion, they might be slightly less.
Summarize the hybridizations: the carbonyl oxygen is sp2, the hydroxyl oxygen is sp3, and the nitrogen is sp3 hybridized, with bond angles around nitrogen slightly less than 109.5 degrees.

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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 concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate the bonding requirements of atoms in a molecule. In the case of glycine, the nitrogen atom typically undergoes sp3 hybridization due to its four substituents, while the oxygen atoms may exhibit sp2 hybridization due to their involvement in double bonds with carbon.
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Hybridization

Bond Angles

Bond angles are the angles formed between adjacent bonds in a molecule, which are influenced by the hybridization of the central atom. For sp3 hybridized atoms, the ideal bond angle is approximately 109.5 degrees, while sp2 hybridized atoms have bond angles around 120 degrees. Understanding these angles helps predict the molecular geometry of glycine.
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Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They provide a visual representation of the arrangement of electrons and help in determining the hybridization and bond angles by illustrating how atoms are connected and the distribution of electron density in the molecule.
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