Chapter 13, Problem 19P

Anethole, the major constituent of anise oil, is used in licorice-flavored sweets and flavored brandy. Answer the following questions using the ball-and-stick model of anethole.

1. What is the molecular formula of anethole?

Identify the functional groups.

Label the carbon-carbon double bond as cis or trans.

Draw the structure of anethole and label each carbon as trigonal planar or tetrahedral.

Interpretation Introduction

(a)

Interpretation:

The molecular formula of anethole should be determined.

Concept Introduction:

The numbers and kinds of atoms present in a molecule of a compound are given by a formula said to be a molecular formula. This formula of a molecule gives the definite number of atoms of each element present in the compound.

Answer to Problem 19P

The molecular formula of anethole is C₁₀H₁₂O.

Explanation of Solution

The given ball-and-stick model of anethole is:

  

In ball-and-stick model, the black ball represents carbon, C atom, white ball represents hydrogen, H atom, and red ball represents oxygen, O atom.

The number of each atom in the ball-and-stick model is:

Carbon atoms = 10

Hydrogen atoms = 12

Oxygen atom = 1

Thus, the molecular of anethole is C₁₀H₁₂O.

Interpretation Introduction

(b)

Interpretation:

The functional group(s) in anethole should be determined.

Concept Introduction:

A group of atoms or an atom which is responsible for the characteristic reactions of a particular compound is said to be the functional group. Every functional group shows distinctive chemical properties irrespective to the moiety to which it is attached.

Answer to Problem 19P

The functional group(s) in anethole is ether.

Explanation of Solution

The given ball-and-stick model of anethole is:

  

When the oxygen atom is connected to two alkyl or aryl groups with general formula R-O-R' such class of compounds is known as ether.

Since, in anethole compound the oxygen atom is bonded to an aryl and an alkyl group so, the functional group(s) in anethole is ether.

Interpretation Introduction

(c)

Interpretation:

The carbon-carbon double bond in anethole should be labeled as cis or trans.

Concept Introduction:

The molecule with same molecular formula and connectivity but differ in spatial arrangements of atoms in the molecule are said to be geometric isomers of each other.

Answer to Problem 19P

The carbon-carbon double bond in anethole is labeled as trans.

Explanation of Solution

The given ball-and-stick model of anethole is:

  

Geometric isomerism, or cis-trans, isomerism is most common in alkenes. The two forms exist due to no free rotation about carbon-carbon double bond. It exists only when the double bonded carbon atoms are joined to two different groups or atoms.

In cis- isomer, the two identical groups or atoms are close to each other whereas in trans- isomer two identical groups or atoms are farther apart.

Since, in the given molecule the groups attached to carbon-carbon double bonded are farther apart from each other so, the carbon-carbon double bond in anethole is trans.

Interpretation Introduction

(d)

Interpretation:

The structure of anethole should be drawn and each carbon should be labeled as trigonal planar or tetrahedral.

Concept Introduction:

In structural formula, the bonding and type of bonds which holds the atoms in molecule together are shown.

Answer to Problem 19P

The structure of anethole is:

  

Labelling of each carbon is:

  

Explanation of Solution

The given ball-and-stick model of anethole is:

  

In ball-and-stick model, the black ball represents carbon, C atom, white ball represents hydrogen, H atom, and red ball represents oxygen, O atom.

So, the structure of anethole is:

  

In the structure of anethole, there are 10 C atoms, 2 of which them are in CH₃- groups which has four electron groups around the central carbon atom, so the electron group arrangement is tetrahedral, sp³hybridized. The 8 carbon atoms have three electron groups around the central carbon atom, so the electron group arrangement is trigonal planar, sp²hybridized.

Thus, the electron group arrangement of all the 10 carbon atoms in anethole is: