Chapter 2, Problem 2.2P

Interpretation Introduction

Interpretation:

Molecular geometry and electron geometry about each non-hydrogen atom in the given molecule is to be predicted using VSEPR theory.

Concept introduction:

Electron geometry and molecular geometry of molecules are determined by using Valence shell electron pair repulsion (VSEPR) theory. According to VSEPR theory, electron geometry describes the orientation of the electron groups about a particular atom and molecular geometry describes the arrangement of atoms about a particular atom.

The number of electron pairs describes the electron and molecular geometry. If all the electron pairs are bonds, then the molecular geometry is the same as the electron geometry. Electron geometry is different from molecular geometry if some electron groups are present as lone pairs. The bond angle depends on the electron geometry around the atom.

Electron geometry and molecular geometry from the number of electron pairs and bond angle according to VSEPR theory are as follows:

Number of Electron Groups	Number of Bonds	Number of Lone Pairs	Bond Angle (o)	Electron Geometry	Molecular Geometry
2	2	0	180	Linear	Linear
3	3	0	120	Trigonal planar	Trigonal planer
3	2	1	120	Trigonal planar	Bent
4	4	0	109.5	Tetrahedral	Tetrahedral
4	4	0	180	Linear	Linear
4	2	2	109.5	Tetrahedral	Bent

Answer to Problem 2.2P

According to VSEPR theory, the electron and molecular geometry about each of the non-hydrogen atom in the structure is as follows:

Oxygen = Electron geometry is tetrahedral while molecular geometry is bent.

C1 carbon atom = Electron geometry is tetrahedral while molecular geometry is also tetrahedral.

C2 and C3 carbon atoms = Electron geometry is linear while molecular geometry is also linear.

Explanation of Solution

The given structure for $\text{prop-2-yn-1-ol}$ is:

The structure showing all the atoms and lone pairs is:

There are four non-hydrogen atoms in the above structure. They are numbered from 1 to 4.

There are four groups of electrons around the oxygen atom: two lone pairs of electrons and two single bonds. According to VSEPR theory, its electron geometry is tetrahedral, and its molecular geometry is bent.

There are four groups of electrons around the C1 carbon: four single bonds and no lone pairs of electrons. According to VSEPR theory, its electron geometry is tetrahedral, and its molecular geometry is also tetrahedral.

There are two groups of electrons around the C2 carbon: one triple bond, and one single bond, and no lone pairs of electrons. According to VSEPR theory, its electron geometry is linear, and its molecular geometry is also linear.

There are two groups of electrons around the C3 carbon: one triple bond, one single bond, and no lone pairs of electrons. According to VSEPR theory, its electron geometry is linear, and its molecular geometry is also linear.

Conclusion

The electron geometry and molecular geometry about each non-hydrogen atom in the given molecule is predicted on the basis of VSEPR chart.