Question

Write the chemical structures for each compound listed. (a) 1 -Hexene (b) 3 -Methyl-1-butane (c) 2, 4-Hexadiene (d) 1-Iodo-2-methy1-2-pentene (e) 2-Chloro-3-methy1-2-hexane (f) 6,6 -Dibromo-5-methy1-5-ethy1-2,3-heptadiene

Short answer

(a) 1-Hexene: \[ \text{CH}2\!=\!\text{CH(CH}_2)_4\text{CH}_3 \] (b) 3-Methyl-1-butane: \[\text{CH}_3\text{-CH}_2\text{-C(CH}_3\text{)CH}_3\] (c) 2, 4-Hexadiene: \[\text{CH}_2=\text{CHCH}=\text{CH(CH}_2)_2\text{CH}_3\] (d) 1-Iodo-2-methy1-2-pentene: \[\text{CH}_2\!=\!\text{C(ICH}_2)_2\text{CH}_3\] (e) 2-Chloro-3-methy1-2-hexane: \[\text{CH}_3\text{-CH(C}l\text{)-C(CH}_3\text{)(CH}_2)_3\text{CH}_3\] (f) 6,6-Dibromo-5-methy1-5-ethy1-2,3-heptadiene: \[\text{CH}_2=\text{CHCH}=\text{C(C}_{2}\text{H}_5\text{)(CBr}_2\text{)CH(CH}_3\text{)CH}_2\text{CH}_3\]

Step-by-step solution

(a) 1-Hexene

1-Hexene is an alkene with six carbon atoms and a double bond at carbon 1. The structure can be drawn as: \[ \text{CH}2\!=\!\text{CH(CH}_2)_4\text{CH}_3 \]

(b) 3-Methyl-1-butane

3-Methyl-1-butane is a hydrocarbon with a main chain of four carbon atoms (butane) and a methyl group at carbon 3. The structure can be drawn as: \[\text{CH}_3\text{-CH}_2\text{-C(CH}_3\text{)CH}_3\]

(c) 2, 4-Hexadiene

2, 4-Hexadiene is an alkene with six carbon atoms and double bonds at positions 2 and 4. The structure can be drawn as: \[\text{CH}_2=\text{CHCH}=\text{CH(CH}_2)_2\text{CH}_3\]

(d) 1-Iodo-2-methy1-2-pentene

1-Iodo-2-methy1-2-pentene is a iodo-substituted alkene with five carbons in the main chain and a double bond at carbon 2. Additionally, there is an iodine atom at carbon 1 and a methyl group at carbon 2. The structure can be drawn as: \[\text{CH}_2\!=\!\text{C(ICH}_2)_2\text{CH}_3\]

(e) 2-Chloro-3-methy1-2-hexane

2-Chloro-3-methy1-2-hexane is an alkane with six carbons in the main chain and a chlorine atom at position 2. Additionally, there is a methyl group at carbon 3. The structure can be drawn as: \[\text{CH}_3\text{-CH(C}l\text{)-C(CH}_3\text{)(CH}_2)_3\text{CH}_3\]

(f) 6,6-Dibromo-5-methy1-5-ethy1-2,3-heptadiene

6,6-Dibromo-5-methy1-5-ethy1-2,3-heptadiene is an alkene with a main chain of seven carbon atoms and double bonds at carbons 2 and 3. Additionally, there are bromine atoms at carbon 6, a methyl group at carbon 5, and an ethyl group at carbon 5 as well. The structure can be drawn as: \[\text{CH}_2=\text{CHCH}=\text{C(C}_{2}\text{H}_5\text{)(CBr}_2\text{)CH(CH}_3\text{)CH}_2\text{CH}_3\]

Key concepts

Alkenes

Alkenes are a noteworthy group of hydrocarbons which contain at least one carbon-carbon double bond (C=C). The presence of this double bond is fundamental to their reactivity and helps differentiate them from alkanes, which only have single bonds between carbon atoms. In IUPAC nomenclature, alkenes are typically identified by replacing the -ane suffix of an alkane with -ene. This alerts the chemist that the compound contains a double bond. The position of this bond is indicated by the lowest possible number in the carbon chain. For instance, in 1-hexene, the double bond is between the first and second carbon atoms, which greatly influences the compound's chemical properties.
Alkenes tend to be more reactive than alkanes due to the higher energy associated with the double bond, and they readily participate in reactions such as hydrogenation, halogenation, and polymerization. This reactivity makes them very important in the petrochemical industry, particularly in the synthesis of plastics and other polymers.

Hydrocarbons

Hydrocarbons form the basic building blocks of organic chemistry. They are compounds composed entirely of hydrogen and carbon atoms. Alkanes, alkenes, and alkynes (those with at least one carbon-carbon triple bond) are the three main types of hydrocarbons. These substances differ in their bonding and structural arrangements, leading to a broad spectrum of physical and chemical properties.
The simplest form of hydrocarbons are alkanes, which are saturated and contain only single bonds between carbon atoms. When a hydrocarbon chain has a branching group, it is called a branched hydrocarbon. For example, 3-methyl-1-butane has a four-carbon straight chain with a single methyl group attached to the third carbon, making it a branched alkane.
This class of compounds is fundamental in chemistry due to their prevalence in fuels, such as propane and butane, and their role as precursors to more complex molecules in organic synthesis.

Halogenated Compounds

Halogenated compounds are organic molecules that contain one or more halogen atoms (fluorine, chlorine, bromine, iodine) incorporated into their structure. These atoms can significantly alter the compound's properties, such as boiling points, reactivity, and solubility in water. A prime example includes 2-chloro-3-methyl-2-hexane, where chlorine is attached to the second carbon of a six-carbon chain.
In these compounds, the halogens are often used as functional groups to impart specific chemical behaviors. Halogenation reactions, whereby halogen atoms are added to hydrocarbons, are valuable in processes such as the synthesis of pharmaceuticals, agrochemicals, and refrigerants.

• Halogen atoms can make compounds more reactive, providing useful properties for various chemical applications.
• The position of the halogen affects the compound's reactivity and how it participates in substitution or elimination reactions.

Understanding the properties of halogenated compounds is crucial for predicting their reactions and applications in industry and commerce.

Organic Nomenclature

Organic nomenclature is a systematic way to name organic chemical compounds as per the guidelines laid out by the International Union of Pure and Applied Chemistry (IUPAC). This system ensures a unique and universally accepted method for naming compounds. The nomenclature involves identifying the longest carbon chain, assigning numbers to the carbon atoms, and identifying functional groups and substituents.
For example, in 2, 4-hexadiene, 'hex' indicates a six-carbon chain, 'diene' signifies the presence of two double bonds, and '2, 4' specifies their positions. The structure of a compound informs not just its name but hints at its chemical behavior and reactivity.

• The primary goal of this nomenclature is to provide clear, unambiguous names for chemical compounds.
• Correct naming is essential for communication and documentation in the scientific community.

By mastering organic nomenclature, chemists can accurately describe complex molecular structures and ensure effective collaboration across the globe.