20 - 3/7/2012 From an understanding of the relative...

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Unformatted text preview: 3/7/2012 From an understanding of the relative stabilities of the species involved, what is an approximate Keq of the following equilibrium? If the Keq ~ 1 how can esters be prepared in high yield (100%) from alcohols and acids? + HOCH3 + H 2O O O CH3 H H C H C O H HOH + H H C H C O + HOCH3 ester acid A. 1 B. 2 C. 3 D. 1 and 2 E. 2 and 3 F. 1 and 3 Are there significant differences in the bond strengths of the reactants compared to the products? A. yes B. no 1. Remove the water. 2. Use a transition metal catalyst. 3. Use an enzyme. From an understanding of the relative stabilities of the species involved, what is an approximate Keq of the following equilibrium? How can esters be prepared from alcohols and acids? + HOCH3 + H 2O benzene 100% O O CH3 H H C H C O H HOH + H H C H C O + HOCH3 ester acid Are there significant differences in resonance stabilization of the reactants compared to the products? A. yes B. no benzene + H2O H2O From an understanding of the relative stabilities of the species involved, what is an approximate Keq of the following equilibrium? How can esters be prepared from alcohols and acids? + HOCH3 + H 2O benzene 100% O O CH3 H H C H C O H HOH + H H C H C O + HOCH3 ester A. about 1.0 Is the top layer benzene? A. yes B. no benzene H2O acid B. much greater than 1.0 C . much less than 1.0 H2O 1 3/7/2012 Esters can be hydrolyzed to acids under acidic conditions. O H H C H C O H C O + O H H H H H C H C O H + H O H C What is the structure of the 3rd reasonable intermediate of the reaction mechanism? H H O H H C H C O H C H H + O H O H H H H C H C O H + H O H C H H H H How can this equilibrium be adjusted to favor the carboxylic acid? O H H C H C H H C H H H H H C H O C O H O H H O H H C H H C H H H H H C O C O H O H H H H H C H O H H C H C H H H H H C H O C H H O O 1. Add excess water. 2. Use a transition metal catalyst. 3. Use an enzyme. H H C H C O H H C H O C O H H O C O H H A B C What is the first reasonable intermediate of the reaction mechanism? O H H C H C O H C O + O H H H H H C H C O H + H O H C Does the H play a similar role as a lipase in catalyzing this reaction? A. yes B. no O H H C H C O H C H H + O H O H H H H C H C O H + H O H C H H H H H H O H H C H C H H C H H O H H C H C H H C H H H H C H H O C O H O H H C H H H H C H O C O H O H H C H H H H H C H O C H H O O O O H H C H C O H H C H H O H H C H C H H C H H O Lipase is an enzyme that catalyzes the formation or cleavage (hydrolysis) of fats (lipids). Lipases are a subclass of the esterases. (wikipedia def.) A B C What is the 2nd reasonable intermediate of the reaction mechanism? O H H C H C O H C O + O H H H H H C H C O H + H O H C What is the mechanism of the following reaction? H H H H O H H C H C H H C H H H H C H H H C O C O H O H H C H H O H H H C H O C O H O H H H H H C H C O O H H C H C O H H C H H A B C 2 3/7/2012 What functional group defines a lipid? lipid A. double bond B. ester How does a lipase catalyze the hydrolysis of an ester? lipid tryglyceride The hydrolys of lipids can be catalyzed by enzymes. histidine Hepatic lipase aspartic acid Hepatic lipase glycerol fatty acids the active site of a lipase How does a lipase catalyze the hydrolysis of an ester? lipid Are these the correct ionization states for the products at pH = 7.2? A. yes B. no lipid histidine aspartic acid Hepatic lipase a protein histidine aspartic acid the active site of a lipase the active site of a lipase Are these the correct ionization states at pH = 7.2? A. yes B. no lipid Are these the correct ionization states for the products at pH = 7.2? A. yes B. no lipid histidine aspartic acid Hepatic lipase histidine aspartic acid pKa (conjugate base) pKa = 4.0 = 6.5 the active site of a lipase 3 3/7/2012 What common consumer product contain lipases? lipid What is the equilibrium constant of the following reaction? + + A. about 1.0 B. much greater than 1.0 C . much less than 1.0 4 ...
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This note was uploaded on 03/27/2012 for the course CHE 322 taught by Professor Staff during the Spring '08 term at SUNY Stony Brook.

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