Question

Write the condensed structural formulas for as many alkenes and alkynes as you can think of that have the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{10}\).

Short answer

The condensed structural formulas for alkenes and alkynes with the molecular formula C6H10 are as follows: 1. Alkenes: a) Two double bonds in the carbon chain: CH2=CHCH=CHCH2CH3 (1,3-hexadiene) b) One double bond and one ring: C6H9(CH3) (methylcyclopentene) 2. Alkynes: a) One triple bond in the carbon chain: HC≡CCH2CH2CH2CH3 (1-hexyne)

Step-by-step solution

Identify the type of hydrocarbon

Alkenes are hydrocarbons containing at least one double bond (C=C) in their structure, while alkynes contain at least one triple bond (C≡C). In this exercise, we are considering both alkenes and alkynes with the molecular formula C6H10.

Calculate the degrees of unsaturation

To evaluate possible isomers, we can use the formula of calculating the degrees of unsaturation (DU): \[DU = \dfrac{2C - (H + N - X)}{2} + 1\] Where C is the number of carbon atoms, H is the number of hydrogen atoms, N is the number of nitrogen atoms, and X is the number of halogen atoms. In this case, the molecular formula is C6H10 with no nitrogen or halogen atoms. Plugging the values into the formula, we get: \[DU = \dfrac{2(6) - (10 - 0 + 0)}{2} + 1 = 3\]

Identify the possible isomers

Since we found out that there are three degrees of unsaturation, we will now find out the isomers for alkenes and alkynes: 1. Alkenes: a) Two double bonds in the carbon chain: \(\mathrm{H}_{2}\mathrm{C}=\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}=\mathrm{C}\mathrm{H}\mathrm{C}\mathrm{H}_{2}-\mathrm{C}\mathrm{H}_{2}\mathrm{C}\mathrm{H}_{3}\) (1,3-hexadiene) b) One double bond and one ring: \(\mathrm{C}_{5}\mathrm{H}_{8}+ \mathrm{C}\mathrm{H}_{2}=\mathrm{C}_{6}\mathrm{H}_{10} \) (methylcyclopentene) 2. Alkynes: a) One triple bond in the carbon chain: \(\mathrm{H}\mathrm{C}\!\equiv\!\mathrm{C}\mathrm{C}\mathrm{H}_{2}-\mathrm{C}\mathrm{H}_{2}\mathrm{C}\mathrm{H}_{2}\mathrm{C}\mathrm{H}_{3}\) (1-hexyne)

Write down the condensed structural formulas

Based on the identified isomers in the previous step, the condensed structural formulas for alkenes and alkynes with the molecular formula C6H10 are as follows: 1. Alkenes: a) Two double bonds in the carbon chain: CH2=CHCH=CHCH2CH3 (1,3-hexadiene) b) One double bond and one ring: C6H9(CH3) (methylcyclopentene) 2. Alkynes: a) One triple bond in the carbon chain: HC≡CCH2CH2CH2CH3 (1-hexyne) These are various isomers of alkenes and alkynes with the molecular formula C6H10. Note that there might be other isomers, but these are the major ones to consider.

Key concepts

Degrees of Unsaturation

Understanding the degrees of unsaturation is crucial for predicting the structures of organic molecules. Degrees of unsaturation, also known as 'index of hydrogen deficiency' or simply 'unsaturation number', indicate how many molecules of hydrogen are missing from the structure that could make it a fully saturated hydrocarbon.

For a hydrocarbon, a fully saturated structure has single bonds only, with each carbon atom forming four single bonds. Degrees of unsaturation are calculated with the formula: \[\begin{equation}DU = \frac{2C - (H + N - X)}{2} + 1\end{equation}\]where C represents the number of carbon atoms, H is the number of hydrogens, N is the number of nitrogens, and X is the number of halogens in the molecule. With each unit of unsaturation, a hydrocarbon loses two hydrogens because a double bond is introduced, or even four when a ring or triple bond is formed.

For example, the molecular formula C6H10, has three degrees of unsaturation. This indicates that compared to a completely saturated hydrocarbon with six carbons, it could have three double bonds, or a double bond and a ring, or one triple bond, and so on.

Hydrocarbon Isomers

The concept of hydrocarbon isomers is fascinating and essential in organic chemistry. Isomers are compounds that have the same molecular formula but differ in the arrangement of their atoms, resulting in different structures and properties.

Isomers can be divided into several types, but two primary categories are structural isomers and stereoisomers. Structural isomers, also known as constitutional isomers, vary in the covalent arrangements of their atoms. For example, considering the formula C6H10, structural isomers could include straight-chain alkenes, branched-chain alkenes, cycloalkanes with side chains, and more.

Stereoisomers have the same molecular formula and sequence of bonded atoms (constitution), but they differ in the three-dimensional orientations of their atoms in space. However, in the context of C6H10, since we're dealing with simple hydrocarbons, our main focus is on structural isomers.

Molecular Formula C6H10

The molecular formula C6H10 is a general representation for several hydrocarbons that can have multiple structural forms. When tackling problems involving C6H10, one can analyze the formula to predict possible structures based on the degrees of unsaturation and knowledge of organic compound nomenclature.

This formula indicates that for every six carbon atoms, there are ten hydrogen atoms. This hydrogen-to-carbon ratio suggests that the compounds will have areas of unsaturation (double or triple bonds, or rings). Because the number of hydrogen atoms is less than what would be expected in a saturated hydrocarbon, which for six carbons would be C6H14, we must consider the creation of double or triple bonds or rings to comply with the rule of hydrogen deficiency.

The molecular formula C6H10 could represent different alkenes and alkynes, such as hexenes with one double bond, hexadienes with two double bonds, cyclohexenes which are cyclic compounds with one double bond, or hexynes with a triple bond. These variations allow for a plethora of structural formulas, each with its own unique chemical properties.