Chapter 2, Problem 2.32P

Interpretation Introduction

Interpretation:

The electron geometry for each indicated atom in the structure of Brassinolide is to be identified. Wherever applicable, the atom’s molecular geometry and bond angles are described.

Concept introduction:

According to the VSEPR theory, the geometry is identified based on groups attached to the central atom. The electron geometry depends on the total number of electrons groups attached to the central atoms. The molecular geometry is decided by the total number of bonded atoms or groups to the central atom. The bond angle is calculated based on the electron geometry of the molecule.

Answer to Problem 2.32P

Type	Atom	Electron Geometry	Molecular Geometry	Bond Angle
(a)	C	Tetrahedral	Tetrahedral	${109.5}^0$
(b)	C	Tetrahedral	Tetrahedral	${109.5}^0$
(c)	C	Trigonal Planar	Trigonal Planar	${120}^0$
(d)	O	Trigonal Planar	Trigonal Planar	${120}^0$
(e)	O	Tetrahedral	Bent	${104.5}^0$

Explanation of Solution

The Lewis structure is drawn based on the total valence electrons in the structure. Carbon atom has four valence electrons, hydrogen has one valence electrons and oxygen has six valence electrons. Hydrogen atoms completed its duet. We need to add lone pairs on the oxygen atom to completes octet.

The atoms are shown with alphabets. The electron geometry and molecular geometry based on a number of electrons groups and bonding groups attached to it respectively is to be written.

1. The electron geometry and molecular geometry of Carbon in ${\text{-CH}}_{\text{3}}$ group.

   There are four groups of electrons around the carbon atom, one single bond with carbon and three single bonds with hydrogen atoms. Central carbon atom has no lone pairs on it. According to VSEPR theory, its electron geometry and its molecular geometry is tetrahedral. For tetrahedral geometry, the bond angle is ${109.5}^0$.

2. The electron geometry and molecular geometry of Carbon atom.

   There are four groups of electrons around the carbon atom, one single bond with hydrogen and three single bonds with carbon atoms. Central carbon atom has no lone pairs on it. According to VSEPR theory, its electron geometry and its molecular geometry is tetrahedral. For tetrahedral geometry, the bond angle is ${109.5}^0$.

3. The electron geometry and molecular geometry of Carbon atom.

   There are three groups of electrons around the carbon atom, one single bond with oxygen, one single bond with a carbon atom and one double bond with oxygen atoms. Central carbon atom has no lone pairs on it. According to VSEPR theory, its electron geometry and its molecular geometry is trigonal planar. The bond angle for tetrahedral geometry is ${120}^0$.

4. The electron geometry and molecular geometry of Oxygen atom.

   There are three groups of electrons around the oxygen atom - one double bond with carbon atom and two lone pairs of electrons. According to VSEPR theory, it has trigonal planar electron geometry and molecular geometry. The bond angle for tetrahedral geometry is ${120}^0$.

5. The electron geometry and molecular geometry of Oxygen in $\text{-OH}$ group.

   There are four groups of electrons around the oxygen atom, one single bond with hydrogen, one single bond with carbon and two lone pairs on it. According to VSEPR theory, its electron geometry is tetrahedral and its molecular geometry is bent. The bond angle of tetrahedral geometry is ${104.5}^0$.

Conclusion

According to VSEPR theory, the electron geometry and molecular geometry is identified.