Q.26 - An Introduction to General, Organic, and Biological Chemistry

Question

Ionone is a compound that gives violets their aroma. The small, edible, purple flowers of violets are used in salads and to make teas. Liquid ionone has a density of

$0.935 g/mL$

a. What functional groups are present in ionone?

 b. Is the double bond on the side chain cis or trans? 

c. What are the molecular formula and molar mass of ionone? 

d. How many moles are in $2.00 mL$ of ionone ?

e. When ionone reacts with hydrogen in the presence of a platinum catalyst, hydrogen adds to the double bonds and converts the ketone group to an alcohol. Draw the condensed structural formula and give the molecular formula for the product. 

f. How many milliliters of hydrogen gas at STP are needed to completely react with $5.00 mL$ of ionone?

Step-by-Step Solution

Answer

Our required answers are:

1. Ketonic Group is present
2. Cis

       c.Molecular Formula= ${\mathrm{C}}_{13}{\mathrm{H}}_{20}\mathrm{O}$; Molecular Mass=$192$

      d.Moles of ionone= $0.0097$

       e.The structure is: 

     

f. When it reacts with ketone $450ml$ will be needed.

Part (a) Step 1: Given Information

We need to tell which functional groups are present in ionone 

Part(a) Step 2: Explanation

From structure of ionone we can conclude that it is an aromatic compound with ketone as its functional group present in side chain of compound.

Part (b) Step 1: Given Information

We need to tell whether the double bond on the side chain is cis or trans in ionone.

Part(b) Step 2: Explanation

Double bond on side chain is cis as for side chain double bond ketonic group and ring are acting as functional group and they are on same side of double bond which satisfies definition of cis isomers.

Part (c) Step 1: Given Information

We need to specify the molecular formula and molar mass of ionone 

Part(c) Step 2: Explanation

Ionone consists of $20$ hydrogen atoms, $1$ oxygen atom and $13$ carbon atoms. So molecular formula of ionone comes out to be ${\mathrm{C}}_{13}{\mathrm{H}}_{20}\mathrm{O}$.

Molecular mass= $$\begin{gathered} (13\times 12)+ (20\times 1) +916\times 1) \\ =192 \end{gathered}$$

Hence, molecular mass of ionone is $192 g/mol$

Part (d) Step 1: Given Information

We need to calculate moles of ionone in $2.00 mL$ of it.

Part(d) Step 2: Explanation

Mass of ionone in $2.00 mL$= $Volume\times Density= 2 mL\times 0.935 g/mL=1.87 g$

Moles = $\frac{Given mass}{Molecular mass}= \frac{1.87}{192}= 0.0097$moles

Hence, $0.0097$ moles of ionone is present in $2.00 mL$.

Part (e) Step 1: Given Information

We have to give the structural formula of ionone when reacted with hydrogen.

Part(e) Step 2: Explanation

When ionone reacts with hydrogen in the presence of a platinum catalyst, hydrogen adds to the double bonds and converts the ketone group to an alcohol.

The structure is :

Part (f) Step 1: Given Information

We have to say how many millilitres it takes to react with ketone.

Part(f) Step 2: Explanation

When it reacts with ketone:

$$\begin{gathered} {\mathrm{C}}_{13}{\mathrm{H}}_{20}\mathrm{O}+{\mathrm{H}}_2\to {\mathrm{C}}_{13}{\mathrm{H}}_{21}\mathrm{OH} \\ \frac{m}{Mr}=\frac{4.675 g}{192 g/\text{ mole }}=0.02 \text{ mole } \\ V\left(H_2\right)=n·Vm \\ =0.02 \text{ mole }\times 22.414 L/mole \\ =0.45L \\ =450 mL \end{gathered}$$