Question

(a) Is the compound \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}\) saturated or unsaturated? Explain. (b) What is wrong with the formula \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}=\mathrm{CH}_{3} ?\)

Short answer

(a) The compound \( CH_{3}CH=CH_{2} \) is unsaturated, as it contains a carbon-carbon double bond (C=C). (b) The issue with the formula \( CH_{3}CH_{2}CH=CH_{3} \) is that the third and fourth carbon atoms do not satisfy carbon's valency requirement of four bonds. This can be corrected to \( CH_{3}CH_{2}CH_{2}CH_{3} \) or \( CH_{3}CH_{2}CH=CH_{2} \), which fulfill the valency requirement for all carbon atoms in the molecule.

Step-by-step solution

Part (a): Determine if the compound is saturated or unsaturated

First, let's review the definitions of saturated and unsaturated hydrocarbons. A saturated hydrocarbon is a molecule in which all carbon-carbon (C-C) bonds are single bonds. An unsaturated hydrocarbon is a molecule containing at least one carbon-carbon double (C=C) or triple (C≡C) bond. The given compound is CH3CH=CH2. We see that there is a carbon-carbon double bond (C=C) present in the molecule. Since there is a double bond, the compound falls under the category of unsaturated hydrocarbons. So, the compound CH3CH=CH2 is unsaturated.

Part (b): Identify the issue with the formula CH3CH2CH=CH3

To check if there is any issue with the formula CH3CH2CH=CH3, let's look into the valency of carbon atoms present in the molecule. Carbon has a valency of 4, which means it can form a total of 4 bonds with other atoms. Let's analyze each carbon atom in the given formula to ensure that they fulfill their valency requirement: 1. The first carbon (in CH3) is connected to three hydrogen atoms and one carbon atom, so it forms 4 bonds (3 with hydrogen and 1 with carbon) which satisfy the valency requirement of carbon. 2. The second carbon (in CH2) is connected to two hydrogen atoms and two carbon atoms, forming a total of 4 bonds (2 with hydrogen and 2 with carbon), which also satisfies the valency requirement of carbon. 3. The third carbon has a double bond with the fourth carbon and a single bond with the second carbon, which results in a total of 3 bonds. This does not satisfy the valency requirement of carbon, which should be 4. 4. Similarly, the fourth carbon (in CH3) is connected to three hydrogen atoms and has a double bond with the third carbon, forming a total of 3 bonds. This also does not fulfill the valency requirement of carbon. So, there is an issue with the given formula CH3CH2CH=CH3 because the third and fourth carbon atoms do not satisfy the valency requirement of carbon. The formula should be corrected to \( CH_{3}CH_{2}CH_{2}CH_{3} \) or \( CH_{3}CH_{2}CH=CH_{2} \) to fulfill the valency requirement for all carbon atoms in the molecule.