Chemistry for Dentistry Students Workbook 14 th week Study of organic compounds II. (p. 177-180.) Written by: Attila Agócs, Zoltán Berente, Gergely Gulyás, Péter Jakus, Tamás Lóránd, Veronika Nagy, Erika Radó-Turcsi, Anikó Takátsy Edited by: Veronika Nagy Name: Group: Date: The following pictogram are used to caution against the danger of handle chemicals: noxious, irritant corrosice toxic flammable oxidizing explosive environmental danger
Pre-lab test questions 1. Give with structural formulas the oxidation of methanol in the human body. Which cofactor is necessary for the reaction? Why is methanol toxic? 2. Give with structural formulas the reaction of ethanol with phosphoric acid. Which type of compound forms? 3. Draw the structural formula of glycerol trinitrate. Which type of compound is it? How does it act in the treatment of coronary diseases? (see. pp. 71) 4. Draw the structural formula of the carbonyl group which represents the real electron distribution. What are the characteristic reactions of oxo-compounds? 5. Compare the behaviour of propanal and that of propanone with oxidizing agents, give equation with structural formulas. 6. Give the equation with structural formulas for the reaction of acetone with hydroxylamine. What kind of reaction occurs? 7. What does 'a Schiff-base' mean? Give an example for the formation of a Schiff-base, give equation with structural formulas. 8. Give the equation with structural formulas for the reaction of acetone with water. What kind of reaction occurs? 9. Draw the structural formula of an aldol. From which starting materials do aldols form? What kind of reaction is this? 10. Give the equation with structural formulas for the oxo-enol tautomerisation of acetone. Indicate the more stable form. 11. Give the equation with structural formulas for the reaction of acetaldehyde with 1 mole of ethanol. What kind of product forms? 12. Give the equation with structural formulas for the reaction of acetaldehyde with 2 moles of ethanol. What kind of product forms? 13. Give examples for primary, secondary, tertiary amines and quaternary ammonium salt. Draw formulas and give their names. 14. Give the equation with structural formulas for the reaction of aniline with hydrochloric acid. Compare the water solubility of aniline and that of the product. 15. Draw the structural formula of carboxyl group and carboxylate group which represents the real distribution of the electrons. 16. Draw the intermolecular hydrogen bonds between two carboxylic acid molecules, use structural formulas. 17. Write the reaction equation for the decarboxylation of butyric acid with structural formulas. 18. How does the negative inductive effect influence the acid strength of the carboxylic acids? Give an example. 19. Give the equation with structural formulas for the reaction of acetic acid with ethanol. What kind of product forms? 20. Give the reaction equation with structural formulas for the base catalyzed hydrolysis of acetamide. 21. Give the reaction equation with structural formulas for the base catalyzed hydrolysis of ethylbutyrate. 22. Draw the formation of γ-butyrolactone from γ-hydroxybutyric acid. 23. Draw the formation of γ-butyrolactam from γ-aminobutyric acid. 24. Draw the structural formulas for tartaric acid and tartarate ion. Which reagent contains a tartarate salt? For the answers see: pp. 177-182. from Laboratory Experiments in Medical Chemistry manual, and the following lecture slides: 34-Alcohols, 36-Aldehydes, ketones, quinones, 37-38-Carboxylic acids and their derivatives, 39-Amines and their derivative 2
Prepare a hot-water bath first Experiments Reactions of oxo compounds Oxidation of an aldehyde on air benzaldehyde Materials: benzaldehyde Procedure: Onto a watch glass place a drop of benzaldehyde. Observe the substance after a half an hour. Give reaction equation with structures. Condensation reaction Materials: 2,4-dinitrophenylhydrazine H 2SO 4 solution, benzaldehyde Procedure: Into a test tubes pour 1 finger of 2,4- dinitrophenylhydrazine H 2SO 4 solution and add 2-3 drops of benzaldehyde to it. Shake the mixture, and let it stand for 5-10 minutes. 2,4-dinitrophenylhydrazine benzaldehyde Give reaction equations and name the products. Comments: Oxo compounds are usually identified and separated by their crystalline condensation products with hydrazine derivatives, which have sharp melting points and are easy to purify. 3
Reducing effect of aldehydes Ammonical silver nitrate test (Tollens-test) Materials: silver nitrate solution, ammonia solution, acetaldehyde, acetone Procedure: a. In a clean test tube pour ammonia solution to a finger of AgNO 3 solution. Add some drops of acetaldehyde to the mixture and place the test-tube into a hot water bath. silver nitrate solution ammonia solution acetone acetaldehyde What do you observe after some minutes? The following reaction happens: H 3C-CHO + 2 [Ag(NH 3) 2] + + 2 OH = H 3C-COOH + 2 Ag + H 2O + 4 NH 3 What is the role of ammonia in the reaction? b. Repeat the experiment with acetone instead of acetaldehyde. How can you explain? Give the formula of acetone. 4
Fehling's test Materials: copper(ii) sulphate solution, potassium sodium tartarate solution, formaline Procedure: In a test-tube mix a finger of CuSO 4 (Fehling I) and the same amount of K-Na-tartrate (Fehling II) solutions. CuSO 4 solution formaline How can you explain? Give reaction equation with structures. b. Add a half finger of formaldehyde solution to the mixture, and place the test-tube into hot water bath. What do you observe after some minutes? Give reaction equation. Comments: Formaline is the aqueous solution of formaldehyde, very toxic, since it causes denaturation of proteins. The reduction of aldehydes may be performed only in alkaline medium. To avoid precipitation of copper(ii) hydroxide K-Na-tartrate is added as a complexing agent to keep copper(ii) ion in solution. In the previous experiment ammonia has a similar role. Acetone is one of the so-called ketone bodies, which appears in higher concentration in blood in diabetes. The breath of patients with diabetes has the characteristic smell of acetone. Legal's test for ketone bodies Materials: acetone, NaOH solution, sodium nitroprusside solution (sodim nitroferricyanide(iii)), concentrated acetic acid Procedure: In a test-tube put some drops of acetone in a finger of distilled water. Add a finger of NaOH solution to it, then 1-2 drops of sodium nitroprusside solution. After the addition of a few drops of acetic acid, the change is more expressive. acetone NaOH soln. Na 2[Fe(CN) 5NO cc. acetic acid List and define the ketone bodies. Comments: The Ketostix urinary ketone test is based on the same reaction. Acetone is one of the so-called ketone bodies, which appears in higher concentration in blood in diabetes. The breath of patients with diabetes has the characteristic smell of acetone. 5
Reactions of amines methylamine HCl Nitrous acid test The reagent is prepared from NaNO 2 by acidification of the NaNO 2 soln. reaction mixture (in situ). Materials: methylamine HCl solution, sodium nitrite solution. Procedure: a. With a primary aliphatic amine To a finger of methylamine HCl solution in a test-tube add a finger of NaNO 2 solution. N 2 gas evolves and an alcohol forms. Complete the equation: CH 3-NH 2 + HNO 2 = Give the reaction equation for the formation of nitrous acid in this experiment. What kind of reaction is this? Theoretical questions and exercises 1. Compare the addition and condensation reactions. Give the differences between them. 2. Pyruvic acid is the final product of break-down of glucose (glycolysis) in living organisms. In the muscle under anaerobic conditions pyruvic acid gives lactic acid, while in certain yeasts it gives acetaldehyde and ethanol. Give these reaction equations with structures. Specify the type of each reaction. 6
3. The last step of glycolysis is the hydrolysis of the phosphate ester of pyruvic acid. Give this reaction equation with structures. Draw the tautomer of the product. Which compound is predominant in the above equilibrium? State your reason. The formation of ATP from ADP (pyrophosphoric acid triphosphoric acid) is followed by a huge incease in free energy. Why can this reaction still happen, what can be its driving force (what makes it exergonic)? 7