Question

The sex attractant of the common housefly is an alkene named cis-tricos-9ene. Draw its structure. (Tricosane is the straight-chain alkane \(\mathrm{C}_{23} \mathrm{H}_{48}\).)

Short answer

Draw cis-tricos-9-ene: 23 C atoms, double bond between C9 and C10, cis configuration.

Step-by-step solution

Understand the base alkane

Tricosane is the straight-chain alkane with the formula \( \mathrm{C}_{23} \mathrm{H}_{48} \), which means it has 23 carbon atoms and 48 hydrogen atoms forming a linear chain.

Identify the functional group

The molecule in question is an alkene, specifically cis-tricos-9-ene, meaning it has a double bond (\( -\mathrm{C} = \mathrm{C}- \)) starting at carbon number 9 in the chain.

Draw the carbon backbone

Draw a chain of 23 carbon atoms in sequence as the backbone for tricosane since it forms the basis for cis-tricos-9-ene.

Introduce the double bond

Convert the bond between the 9th and 10th carbon in the chain from a single bond to a double bond. Ensure that the geometry around the double bond is such that the substituents on each carbon are on the same side, which is characteristic of the 'cis' configuration.

Adjust hydrogen atoms

After introducing the double bond, the total number of hydrogens decreases by two due to the double bond. Adjust the number of hydrogen atoms on the affected carbons (carbon 9 and 10) to maintain proper valency, i.e., each carbon forms four bonds in total.

Verify the structure

Check the structure to ensure it contains a total of 23 carbon atoms, has a cis-double bond at the 9th position, and satisfies the valency for each atom in the molecule.

Key concepts

Alkene Overview

Alkenes are a class of hydrocarbons that contain at least one carbon-carbon double bond (\( -\mathrm{C} = \mathrm{C}- \)). This double bond is what distinguishes alkenes from alkanes, which have only single bonds between carbon atoms. The presence of a double bond means alkenes are unsaturated hydrocarbons, meaning they have fewer hydrogen atoms compared to alkanes with a similar number of carbon atoms.

Alkenes are important in organic chemistry because the reactive nature of the double bond makes them versatile intermediates in chemical reactions. This double bond introduces the possibility for alkenes to undergo various chemical reactions, such as:

• Addition reactions, where new atoms add across the double bond.
• Polymerization, which forms long chains of repeating units.
• Oxidation and reduction reactions that can further modify the hydrocarbon.

Given these properties, alkenes play a crucial role in industrial applications, such as the production of plastics, alcohols, and other important organic compounds.

Understanding Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties, especially reactivity profiles. They are the centers of chemical reactivity in organic molecules. In the context of alkene molecules like cis-tricos-9-ene, the functional group is the carbon-carbon double bond, which is crucial for determining the chemical behavior of the molecule.

The double bond acts as a point of vulnerability in the molecule, allowing for various reaction pathways that can include:

• Electrophilic addition reactions, where electrophiles are attracted to the electron-rich double bond.
• Hydrohalogenation, where hydrogen and halogen atoms are added across the double bond.
• Hydrogenation, where hydrogen is added, saturating the double bond and converting it into a single bond.

By understanding functional groups, chemists can predict how a molecule will react under certain conditions, allowing them to design specific synthesis pathways and understand the molecule’s role in larger reactions and biological systems.

Core Concepts of Organic Chemistry

Organic chemistry is the branch of chemistry concerned with the structure, properties, and reactions of organic compounds, which contain carbon atoms. It is a vast field, covering millions of compounds and complex reactions.

Some fundamental concepts in organic chemistry include:

• The carbon backbone, which forms the structural framework of organic molecules.
• Isomerism, where molecules with the same formula have different structures and properties, such as cis-trans isomerism seen in alkenes.
• Reactivity based on functional groups and the overall molecular structure.

Understanding these principles enables chemists to predict and explain the behavior of organic compounds. Cis-tricos-9-ene, for instance, illustrates these concepts well, as it features the double bonds typical to alkenes and exhibits the cis configuration, affecting its physical properties and reactivity. Such insights are critical for applications ranging from material science to pharmaceuticals.