Question

Ecdysone is the molting hormone (not a pheromone) that encourages the maturation of a larval stage of the silkworm into the pupal stage. It can kill insects by causing premature molting. (a) What general class of compounds is respresented by ecdysone? (b) Identify the chiral centers and assign their absolute configurations where possible. (c) How many products would be produced if ecdysone were reduced by catalytic hydrogenation under conditions that resulted in the uptake of two equivalents of hydrogen? (d) What, if anything, would be the relationship among these compounds?

Short answer

(a) Ecdysone belongs to the general class of compounds called steroid hormones. (b) Without knowing the specific structure of ecdysone, we cannot identify chiral centers and their absolute configurations. (c) The number of products produced by catalytic hydrogenation depends on the double bonds present in the structure. Since the ecdysone structure is not given, we can't calculate the exact number of products produced. (d) The compounds obtained from the hydrogenation of ecdysone would be diastereomers of each other, as they have different configurations at some but not all chiral centers.

Step-by-step solution

Part (a): Identify the general class of compounds represented by ecdysone

Ecdysone is a steroid hormone that plays a crucial role in the development and metamorphosis of insects. The general class of compounds represented by ecdysone is the steroid hormones. These hormones have a specific structure composed of four cycloalkane rings (three cyclohexane rings and one cyclopentane ring) that are fused together.

Part (b): Identify the chiral centers and assign their absolute configurations

To identify the chiral centers in ecdysone, first, we need to recognize the carbon atoms that have four different groups attached to them. Chiral centers are depicted with an asterisk (*) in the structure. Once we identify all the chiral centers, we can use the Cahn-Ingold-Prelog (CIP) system to determine the absolute configuration (R/S) of each carbon. Unfortunately, without knowing the specific structure of ecdysone in this exercise, we cannot identify the chiral centers and determine the absolute configuration of them. In a practical situation, you would be provided with the structure or be able to look it up.

Part (c): Determine the number of products produced by catalytic hydrogenation

If ecdysone is reduced by catalytic hydrogenation under conditions that resulted in the uptake of two hydrogen equivalents, the number of products produced would depend on the reduction of the double bonds present in the structure. Since the ecdysone structure is not given, we can't calculate the exact number of products produced. However, the general approach would be to evaluate the double bond positions and analyze their reduction to single bonds. Each double bond reduced could lead to one or more stereoisomers, depending on the number of chiral centers affected.

Part (d): Analyze the relationship among the obtained compounds

The relationship among the compounds obtained from the hydrogenation of ecdysone would be that they are diastereomers of each other. This is because the hydrogenation process changes the configuration of carbon atoms involved in the double bonds but does not affect the other chiral centers in the molecule. Diastereomers are a type of stereoisomers that are not mirror images of each other.

Key concepts

Steroid Hormones

Steroid hormones are a major class of hormones that play numerous roles in the body. They are characterized by a specific structure made of four cycloalkane rings. This includes three cyclohexane rings and a cyclopentane ring, all fused together. Ecdysone is one such steroid hormone. It is critical in helping insects transition from one stage of development to another, such as from the larval to the pupal stage in silkworms.

These hormones are lipid-soluble, meaning they can easily pass through cell membranes. They typically bind to specific receptors inside the cell, which then activate or deactivate particular genes, affecting the function of the cell. Understanding this category of hormones is essential as they contribute significantly to growth, metabolism, and reproductive processes.

Other well-known steroid hormones include cortisol, testosterone, and estrogen.

Chiral Centers

Chiral centers in molecules refer to carbon atoms that are bonded to four distinct substituents, making them non-superimposable on their mirror image. This is a key concept in stereochemistry, which is crucial for understanding the behavior of molecules like ecdysone.

To determine a chiral center's configuration, we apply the Cahn-Ingold-Prelog (CIP) priority rules, where each substituent is ranked in order of atomic number and connectivity. Once priority is established, the verdict is made for the configuration as either R or S, based on the direction of the priority when viewed along the bond.

Identifying and understanding chiral centers is important because they can greatly affect the biological activity of a hormone or drug. Even a small change in configuration can lead to significant changes in the physiological effects of a compound.

Catalytic Hydrogenation

Catalytic hydrogenation is a chemical reaction that involves the addition of hydrogen (H₂) to a molecule, in the presence of a catalyst like palladium or platinum. This process typically results in the conversion of unsaturated bonds, such as double or triple carbon-carbon bonds, into single bonds.

In the context of ecdysone, hydrogenation would reduce any double bonds present in the molecule. The uptake of two hydrogen equivalents would reduce two double bonds, potentially leading to the formation of new chiral centers and new compounds. Each affected double bond has the potential to create multiple stereoisomers, depending on the number of chiral centers formed.

Catalytic hydrogenation is a significant reaction in industrial chemistry, utilized frequently to convert oils to solid fats and to produce various pharmaceuticals by altering the properties and reactivity of chemical compounds.

Diastereomers

Diastereomers are a type of stereoisomers, which are not mirror images of each other. They occur when molecules have multiple chiral centers, and at least one but not all chiral centers differ in configuration. This is distinct from enantiomers, which are non-superimposable mirror images.

In processes like catalytic hydrogenation of ecdysone, diastereomers may be formed. When double bonds are reduced, the spatial arrangement around newly formed single bonds can differ, leading to the creation of diastereomers. They exhibit different physical properties such as boiling points, solubility, and melting points, facilitating their separation through conventional lab techniques.

Understanding diastereomers is vital in the development and application of chemical reactions as they influence the chemical and biological properties of substances. They are an essential consideration in the pharmaceutical industry for drug synthesis and development.