One of the first drugs to be approved for use in treatment of acquired immune deficiency syndrome (AIDS) was azidothymidine (AZT). Complete the Lewis structure for AZT. a. How many carbon atoms are \(s p^{3}\) hybridized? b. How many carbon atoms are \(s p^{2}\) hybridized? c. Which atom is \(s p\) hybridized? d. How many \(\sigma\) bonds are in the molecule? e. How many \(\pi\) bonds are in the molecule? f. What is the \(\mathrm{N}=\mathrm{N}=\mathrm{N}\) bond angle in the azide \(\left(-\mathrm{N}_{3}\right)\) group? g. What is the \(\mathrm{H}-\mathrm{O}-\mathrm{C}\) bond angle in the side group attached to the five-membered ring? h. What is the hybridization of the oxygen atom in the \(-\mathrm{CH}_{2} \mathrm{OH}\) group?

Step by step solution

01

Draw the Lewis structure for AZT

Let's begin by drawing the complete Lewis structure for azidothymidine (AZT): Azidothymidine (AZT) is composed of a five-membered ring (a pyrimidine ring) with an azide (-N3) group, an -OH group, and a -CH2OH group attached to it. Let's first draw the five-membered pyrimidine ring with the various functional groups attached:  Now, with the Lewis structure complete, we can proceed to answer each of the questions.

02

Identifying sp³ hybridized Carbons

A carbon atom is sp³ hybridized when it is connected to four different atoms. From the structure, we can identify that there are two such sp³ hybridized carbon atoms. They are: 1. The carbon atom connected to two hydrogen atoms, an oxygen atom, and the five-membered ring. 2. The carbon atom in the five-membered ring, connected to an oxygen atom, a nitrogen atom, and two carbon atoms from the ring. a. Therefore, there are two sp³ hybridized carbon atoms in the molecule.

03

Identifying sp² hybridized Carbons

A carbon atom is sp² hybridized when it is connected to three different atoms and has a pi bond with one atom. From the structure, we can identify that there are two such sp² hybridized carbon atoms. They are: 1. The carbon atom in the five-membered ring, connected to a nitrogen atom, a carbon atom, and a double-bonded oxygen atom. 2. The carbon atom in the five-membered ring, connected to a nitrogen atom, a carbon atom, and a double-bonded nitrogen atom. b. Therefore, there are two sp² hybridized carbon atoms in the molecule.

04

Identifying sp hybridized Atom

An atom is sp hybridized when it is connected to two different atoms and has a pi bond. The azide group has a linear N=N=N structure, in which the central nitrogen atom is sp hybridized. c. The sp hybridized atom is the central nitrogen atom in the azide group.

05

Counting σ bonds

Sigma (σ) bonds are single covalent bonds between atoms. To count the number of σ bonds in the molecule, count all single bonds between atoms. There are 21 σ bonds in the molecule. d. There are 21 σ bonds in the molecule.

06

Counting π bonds

Pi (π) bonds are double or triple covalent bonds between atoms. To count the number of π bonds in the molecule, count all double and triple bonds between atoms. There are two double bonds and one triple bond between atoms in the molecule. e. There are three π bonds in the molecule.

07

N=N=N bond angle

The central nitrogen atom in the azide group has linear geometry, which means the bond angle between the three nitrogen atoms is 180°. f. The N=N=N bond angle is 180°.

08

H-O-C bond angle

The carbon atom connected to the side group attached to the ring is sp³ hybridized, which gives it tetrahedral geometry. The H-O-C bond angle in tetrahedral geometry is around 109.5°. g. The H-O-C bond angle is approximately 109.5°.

09

Hybridization of the oxygen atom

The oxygen atom in the -CH2OH group is connected to a carbon atom, a hydrogen atom, and has two lone pairs. This gives it sp³ hybridization. h. The hybridization of the oxygen atom in the -CH2OH group is sp³.

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