ochem 2 lab exam 1

What are Grignard reagents, and why are they important?

Grignard reagents are organomagnesium compounds used to form carbon-carbon bonds, essential for synthesizing alcohols, carboxylic acids, and hydrocarbons due to their strong nucleophilic nature.

What roles do bromobenzene, magnesium, and diethyl ether play in a Grignard reaction?

Bromobenzene forms the phenyl group for the Grignard reagent, magnesium facilitates the carbon-metal bond formation, and diethyl ether stabilizes the Grignard reagent and acts as a solvent.

What is the difference between oxidation and reduction reactions?

Oxidation is the loss of electrons, typically adding oxygen or removing hydrogen; reduction is the gain of electrons, typically adding hydrogen or removing oxygen.

What are the main reagents used in oxidation and reduction reactions in the lab?

Oxidation uses sodium hypochlorite (NaOCl); reduction uses sodium borohydride (NaBH₄) or lithium aluminum hydride (LiAlH₄) as a stronger reducing agent.

What is the difference between kinetic products and thermodynamic products?

Kinetic products form quickly with lower activation energy but are less stable; thermodynamic products form slowly with higher stability and require higher temperatures.

Which product, endo or exo, is the major product in a Diels-Alder reaction and why?

The endo product is the major product due to secondary orbital interactions that stabilize the transition state, following the endo rule.

What is the Diels-Alder reaction?

It’s a [4+2] cycloaddition reaction between a diene and a dienophile, producing a cyclohexene derivative by forming two new carbon-carbon sigma bonds in a concerted, stereospecific manner.

Why is the Diels-Alder reaction a syn addition?

Because the reaction is concerted, all new bonds are formed on the same face of the reactants, resulting in stereospecificity.

Does the Diels-Alder reaction have stereoselectivity?

Yes, it exhibits high stereoselectivity and regioselectivity due to its concerted mechanism, preserving the stereochemistry of the reactants.

How do you calculate the theoretical yield of a reaction?

Determine moles of the limiting reactant, use the stoichiometry of the reaction to calculate moles of product, and convert moles of product to grams using molar mass.

How do you calculate the percent yield of a reaction?

Percent Yield = (Actual Yield / Theoretical Yield) x 100.

What is the purpose of glacial acetic acid and anhydrous sodium sulfate in lab reactions?

Glacial acetic acid enhances reaction efficiency by providing an acidic medium; anhydrous sodium sulfate removes residual water during the workup step.

How does water affect the melting point of semicarbazones?

Water lowers the melting point by introducing impurities, disrupting the crystal lattice structure.