Question

1. If by mistake, chemist used 100% ethanol rather than THF as a solvent, would the synthesis proceed as expected? Why or why not?

2. Why is bromotoluene added dropwise to the reaction flask rather than all at once?

3. Draw a dipole moment (see chapter 1) to explain the polarity of the following Grignard reagent?

MgBr

1. In this reaction we will be heating butadiene sulfone to perform a Diels-Alder reaction. What side product is generated upon heating butadiene sulfone and how will we trap this side product?

2. In most chemical reactions it is a bad idea to create a closed system, that is a system which cannot attenuate to pressure changes. In this reaction what measures are taken to avoid a closed system and why would it be a particularly bad idea to create a closed system for this Diels-Alder reaction?

Answer 1

1. If by mistake, chemist used 100% ethanol rather than THF as a solvent, would the synthesis proceed as expected? Why or why not?

Solution :- In the Grignard reagent experiment the Grignard reagent RMgX is having alkyl group with negative charge that is R^-. This acts as base so it can easily take up the H from the alcohol to form the alkane product so the reaction does not occur as expected. Polar protic solvent is not used in the Grignard reactions so we cannot use the 100% ethanol since it is protic solvent which is not helpful in the Grignard reaction.

2. Why is bromotoluene added dropwise to the reaction flask rather than all at once?

Solution :- Addition of the bromotolune dropwise helps to form the Grignard salt. If the bromotolune is added all time then it may lead to vigorous reaction so to avoid that bromotolune is added dropwise.

1. In this reaction we will be heating butadiene sulfone to perform a Diels-Alder reaction. What side product is generated upon heating butadiene sulfone and how will we trap this side product?

Solution :- The side product formed in the reaction is the SO2 gas which is generated from the butadiene sulfone on heating. Therefore we can trace this by the observing the bubbling in the reaction mixture.

2. In most chemical reactions it is a bad idea to create a closed system, that is a system which cannot attenuate to pressure changes. In this reaction what measures are taken to avoid a closed system and why would it be a particularly bad idea to create a closed system for this Diels-Alder reaction?

Solution :- If the system is closed then gases formed during the reaction would not escape from the system which causes the pressure build up in the system which can cause the explosion of the apparatus. So it is bad idea to use the closed system in the Diels Alder reaction.