Question

                  

What are coumarins? What are the uses of coumarins?

What are coumadins? Draw structure of a popular coumadin and list uses

                                             

In this lab you used Amberlyst, a solid supported acid catalyst. What are the advantages of using a solid supported acid catalyst in comparison to a regular acid catalyst?

                                                 

In this experiment, you recrystallized your product using a two solvent system of ethanol and water. What will happen if you use too much ethanol? What will happen if you add too much water?

                      

              

Answer 1

Coumarins (1-benzopyran-2-one) are chemical compounds in the benzopyrone class of organic compounds found in many plants. Coumarins possess a variety of biological properties, including antimicrobial, antiviral, antiinflammatory, antidiabetic, antioxidant, and enzyme inhibitory activity. This chapter gives an overview of the isolation, structural features, and pharmacological actions of variety of coumarins produced by the African plants. The biosynthetic pathway of coumarins is also discussed in this chapter. We identify 117 coumarins in African plants, of which 48 are new. The pharmacological activities of 54 of these coumarins are reported..

2.In acid catalysis and base catalysis a chemical reaction is catalyzed by an acid or a base. The acid is the proton donor and the base is the proton acceptor, known as Bronsted-Lowry acid and base respectively. Typical reactions catalyzed by proton transfer are esterfications and aldol reactions. In these reactions the conjugate acid of the carbonyl group is a better electrophile than the neutral carbonyl group itself. Catalysis by either acid or base can occur in two different ways: specific catalysis and general catalysis. Many enzymes operate by acid-catalysis.

cid catalysis is mainly used for organic chemical reactions. Many acids can function as sources for the protons. Acid used for acid catalysis include hydrofluoric acid (in the alkylation process), phosphoric acid, toluenesulfonic acid, polystyrene sulfonate, heteropoly acids, zeolites.

Strong acids catalyze the hydrolysis and transesterification of esters, e.g. for processing fats into biodiesel. In terms of mechanism, the carbonyl oxygen is susceptible to protonation, which enhances the electrophilicity at the carbonyl carbon.

Two kinds of acid catalysis are recognized, specific acid catalysis and general acid catalysis.

Specific catalysis

In specific acid catalysis, protonated solvent is the catalyst. The reaction rate is proportional to the concentration of the protonated solvent molecules SH+. The acid catalyst itself (AH) only contributes to the rate acceleration by shifting the chemical equilibrium between solvent S and AH in favor of the SH+ species. This kind of catalysis is common for strong acids in polar solvents, such as water.

S + AH ? SH⁺ + A^?

For example, in an aqueous buffer solution the reaction rate for reactants R depends on the pH of the system but not on the concentrations of different acids.

for recrystallization to work, the substance to be purified must be soluble in the hot solvent but insoluble in the same solvent, cold. You don't want to have too good of a solvent, otherwise you'll still have a solution at room temperature. Water is added to ethanol in this experiment to make it a worse solvent for the brominated acetanilide. (On the other hand, pure water would fail to dissolve the brominated acetanilide even when hot--you don't want to have too poor a solvent either).