Question

Named \(bombykol\), the sex pheromone secreted by the female silkworm moth has the formula \(\mathrm{C}_{16} \mathrm{H}_{30} \mathrm{O}\) and the systematic name \((10 E, 12 Z)\). hexadeca-10,12-dien-1-ol. Draw bombykol showing correct geometry for the two double bonds.

Short answer

Draw a 16-carbon chain with double bonds at positions 10 and 12, using 'E' (opposite) and 'Z' (together) geometry respectively. Add an OH group to the first carbon.

Step-by-step solution

Identify Double Bonds

The systematic name (10E, 12Z)-hexadeca-10,12-dien-1-ol indicates the position and configuration of the double bonds. The numbers 10 and 12 show where the double bonds are located in the carbon chain.

Understand E and Z Notations

The 'E' and 'Z' notations describe the geometry of the double bonds. 'E' stands for 'entgegen' which means 'opposite' in German, and 'Z' stands for 'zusammen' which means 'together'. This tells you how substituents around the double bond are arranged.

Draw the Carbon Backbone

Draw a chain consisting of 16 interconnected carbon atoms. This forms the basic skeleton upon which the double bonds and alcohol group will be added.

Add Double Bonds

Introduce a double bond between carbon atoms 10 and 11 with the 'E' configuration, and another between carbon atoms 12 and 13 with the 'Z' configuration.

Configure E/Z Geometry

For the double bond at positions 10 and 11, ensure that the largest substituents are on opposite sides to display the 'E' configuration. For the double bond at positions 12 and 13, the largest substituents should be on the same side for the 'Z' configuration.

Add Alcohol Group

Attach a hydroxyl group (OH) to the first carbon atom, as indicated by the '-1-ol' in the systematic name.

Key concepts

E/Z isomerism

The terms E/Z isomerism refer to a specific type of stereoisomerism that occurs in double-bonded carbon atoms. Double bonds restrict rotation, creating a situation where different spatial arrangements, called isomers, are possible. The E/Z system classifies these isomers based on the relative positions of the substituents attached to the double-bonded carbons.

- **E isomer (entgegen):** For the E configuration, the major groups attached to each carbon of the double bond are positioned on opposite sides. In the case of bombykol, this means that for the 10,11 double bond, substituents are placed on differing sides of the double bond's longitudinal axis.
- **Z isomer (zusammen):** Conversely, the Z configuration places the major substituents on the same side. In bombykol, the double bond between carbons 12 and 13 holds its largest substituents side by side, reflecting its 'togetherness'.

This naming system grants chemists a clear and concise way to dictate molecular geometry, crucial for understanding chemical behavior.

Organic chemistry

Organic chemistry is the science of carbon-containing compounds, primarily hydrocarbons, and their variations. It encompasses numerous concepts, from molecular structure to reaction mechanisms. Central to organic chemistry is the classification of compounds through functional groups and bond types, both of which are key features in bombykol.

- **Hydrocarbons and Functional Groups:** Bombykol's structure reveals a 16-carbon backbone with two notable features: two double bonds and an alcohol group (-OH). The position and nature of these groups significantly impact the compound's reactivity and interaction.
- **Nomenclature and Systematic Naming:** Providing a unique name, like (10E, 12Z)-hexadeca-10,12-dien-1-ol, allows chemists to identify and communicate molecular details. This name tells us about the number of carbon atoms, position and configuration of double bonds, and functional groups present.

Understanding organic chemistry principles gives insight into the properties and roles these molecules play, such as bombykol acting as a pheromone.

Molecular geometry

Molecular geometry pertains to the 3D arrangement of atoms within a molecule, determining its shape and physical properties. For compounds like bombykol, the geometric arrangement around its double bonds and hydroxyl group is crucial.

- **Impact of Double Bonds:** In bombykol, the double bonds create rigid planar regions due to the p-orbitals' overlap, preventing bond rotation. This rigidity assists in defining the 'E' or 'Z' confirmations, affecting how the molecule interacts with biological systems.
- **Effect of Substituents:** Substituent position influences molecular polarity and interactions. For instance, the placement of the hydroxyl group in bombykol contributes to its solubility and interaction with receptor proteins.

Understanding molecular geometry is vital to predicting a molecule's behavior in chemical reactions and biological interactions, offering insights into its efficacy as a biochemical signal like bombykol.