Question

Suggest products when \(\mathrm{Et}_{3} \mathrm{SnCl}\) reacts with the following reagents: (a) \(\mathrm{H}_{2} \mathrm{O} ;(\mathrm{b}) \mathrm{Na}[\mathrm{Cp}]\) (c) \(\mathrm{Na}_{2} \mathrm{S} ;\) (d) PhLi; (e) Na.

Short answer

Products: (a) \(\mathrm{Et}_3\mathrm{SnOH}\), (b) \(\mathrm{Et}_3\mathrm{SnCp}\), (c) \((\mathrm{Et}_3\mathrm{Sn})_2\mathrm{S}\), (d) \(\mathrm{Et}_3\mathrm{SnPh}\), (e) \(\mathrm{Et}_3\mathrm{SnNa}\).

Step-by-step solution

Reaction with Water

When triethyltin chloride (\(\mathrm{Et}_{3}\mathrm{SnCl}\)) reacts with water, a hydrolysis reaction occurs. The chlorine is replaced by a hydroxide group, resulting in the formation of triethyltin hydroxide: \(\mathrm{Et}_3\mathrm{SnOH}\). The balanced reaction is: \[\mathrm{Et}_3\mathrm{SnCl} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{Et}_3\mathrm{SnOH} + \mathrm{HCl}\].

Reaction with Sodium Cyclopentadienide

When \(\mathrm{Et}_{3}\mathrm{SnCl}\) reacts with \(\mathrm{Na}[\mathrm{Cp}]\), a nucleophilic substitution occurs, where the \(\mathrm{Cl}^-\) is replaced by the cyclopentadienide anion \(\mathrm{Cp}^-\). The product is triethyltin cyclopentadienide \(\mathrm{Et}_3\mathrm{SnCp}\). The reaction is: \[\mathrm{Et}_3\mathrm{SnCl} + \mathrm{Na}[\mathrm{Cp}] \rightarrow \mathrm{Et}_3\mathrm{SnCp} + \mathrm{NaCl}\].

Reaction with Sodium Sulfide

In the reaction of \(\mathrm{Et}_{3}\mathrm{SnCl}\) with sodium sulfide (\(\mathrm{Na}_{2}\mathrm{S}\)), each chlorine atom is replaced by a sulfur atom. The resulting product is triethyltin sulfide (\((\mathrm{Et}_3\mathrm{Sn})_2\mathrm{S}\)). The balanced reaction is: \[2 \mathrm{Et}_3\mathrm{SnCl} + \mathrm{Na}_2\mathrm{S} \rightarrow (\mathrm{Et}_3\mathrm{Sn})_2\mathrm{S} + 2 \mathrm{NaCl}\].

Reaction with Phenyllithium

Phenyllithium (\(\mathrm{PhLi}\)) reacts with \(\mathrm{Et}_{3}\mathrm{SnCl}\) leading to a substitution of the chlorine atom by the phenyl group. The product is triethyltin phenyl (\(\mathrm{Et}_3\mathrm{SnPh}\)). The reaction can be written as: \[\mathrm{Et}_3\mathrm{SnCl} + \mathrm{PhLi} \rightarrow \mathrm{Et}_3\mathrm{SnPh} + \mathrm{LiCl}\].

Reaction with Sodium

When \(\mathrm{Et}_{3}\mathrm{SnCl}\) reacts with sodium metal (\(\mathrm{Na}\)), a substitution reaction occurs where sodium displaces the chlorine. The result is the formation of triethyltin sodium (\(\mathrm{Et}_3\mathrm{SnNa}\)). The balanced reaction is: \[\mathrm{Et}_3\mathrm{SnCl} + \mathrm{Na} \rightarrow \mathrm{Et}_3\mathrm{SnNa} + \mathrm{NaCl}\].

Key concepts

Reaction Mechanisms

Understanding how reactions occur at the molecular level is crucial in chemistry. A reaction mechanism describes the step-by-step process by which reactants transform into products. In organotin chemistry, these mechanisms often involve organometallic compounds like triethyltin chloride (\(\text{Et}_3\text{SnCl}\)) reacting with different reagents.

Let's take hydrolysis as an example. When \(\text{Et}_3\text{SnCl}\) reacts with water, the reaction proceeds through a nucleophilic attack of a water molecule. Here, the oxygen in the water, bearing a partial negative charge, targets the tin center, which is positively polarized due to its bonding with chlorine. This results in the replacement of the chloride ion by a hydroxide ion, forming triethyltin hydroxide (\(\text{Et}_3\text{SnOH}\)).

This is just one type of reaction mechanism. Different reagents can produce a variety of mechanistic pathways, often leading to the displacement of the leaving group (like \(\text{Cl}^-\)) by stronger nucleophiles or more reactive species.

Organometallic Chemistry

Organometallic chemistry is a fascinating branch of chemistry that explores compounds containing bonds between a carbon atom of an organic molecule and a metal. In the context of the original exercise, \(\text{Et}_3\text{SnCl}\) is an organotin compound, as it contains tin bonded to organic ethyl groups.

Organometallic compounds are characterized by their ability to participate in a wide array of chemical reactions, thanks to their unique properties. The metal-carbon bond in these compounds often imparts unusual reactivity patterns. For instance, triethyltin compounds can act as both nucleophiles and electrophiles, depending on the reacting partner.

When \(\text{Et}_3\text{SnCl}\) undergoes reactions such as nucleophilic substitutions, the organometallic nature of the compound is highlighted. The tin center can be attacked by nucleophiles leading to the displacement of the halogen anion and formation of new bonds. This versatility makes organometallic chemistry invaluable in synthetic applications, including the development of pharmaceuticals and agrochemicals.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions are an essential type of chemical reaction where a nucleophile replaces a leaving group in a molecule. In these reactions, the nucleophile, an electron-rich species, targets a positively charged or partially positively charged atom within the substrate.

With \(\text{Et}_3\text{SnCl}\) acting as the substrate, reactions like those described with \(\text{Na[Cp]}\) illustrate nucleophilic substitution. Here, the cyclopentadienide anion (\(\text{Cp}^-\)) acts as the nucleophile, attacking the tin center to replace the chloride ion, generating \(\text{Et}_3\text{SnCp}\).

• In the reaction, \(\text{Cp}^-\) brings its electron pair to form a new bond with tin.
• The chloride ion, being a good leaving group, is displaced.
• This kind of mechanism is typical in SN2 reactions.

Understanding nucleophilic substitution is vital as it plays a central role in synthesizing a vast array of chemical products, offering an efficient pathway to manipulate and create new carbon-metal bonds.