PERKIN REACTION: CONDENSATION REACTION OF AN AROMATIC ALDEHYDE AND AN ACID ANHYDRIDE PDF

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Summary

Cinnamic acid together with cinnamaldehyde are natural products from cinnamon oil. In this
practical, cinnamic acid is synthesized by the Perkin condensation reaction, which involves the
reaction between an acid anhydride (acetic anhydride) and an aromatic aldehyde
(benzaldehyde) c...

Description

Title: Synthesis of cinnamic acid through Perkin reaction Aim: The aim of this research is to synthesize cinnamic acid Abstract: Cinnamic acid plays a vital role in the synthesis of other important compounds and as a precursor for the synthesis of commercial cinnamon esters used in perfumery, cosmetics, and pharmaceutical industries. The aim of this research is to synthesize cinnamic acid using sonochemical methods. Cinnamic acid was synthesized using Perkin reaction by reacting 0.0417mole of benzaldehyde with 0.073 mole of acetic acid anhydride and 0.03 mole of sodium acetate as a catalyst in the Erlenmeyer flask. The colour of the product was white crystalline with 37 % yield and a melting point of 133 + 2º C. Other test were not carried out due to limited time and resource. Introduction: Cinnamic acid together with cinnamaldehyde is natural products from cinnamon oil. In this practical, cinnamic acid was synthesized by the Perkin condensation reaction, which involves the reaction between an acid anhydride (acetic anhydride) and an aromatic aldehyde (benzaldehyde) catalyzed by a base (sodium acetate). The anhydride generates a carbanion due to the influence of the base (sodium acetate), which attacks the carbonyl group of the aldehyde. Then the anhydride group undergoes a process of dehydration and hydrolysis.

Materials:

Figure 1: Overall reaction of the experiment

Equipment: 250-ml round-bottom flask, reflux apparatus, steam distillation apparatus, hot plate or heating mantle, vacuum filtration apparatus, ice-bath, melting point instrument, graduated cylinder, beakers, Erlenmeyer flasks, filter paper Chemicals Benzaldehyde 5.0 g Acetic anhydride 7.5 g Sodium acetate 2.5 g Conc. HCl (for acidification step) Distilled water

Procedure: 1. In a 250 ml round-bottom flask provided with a reflux condenser and a drying tube, 5 g of benzaldehyde 7.5 g of acetic anhydride and 2.5 g of sodium acetate were placed. 2. The reflux was heated for 3 h. It was allowed to cool to r.t and then add 100 ml of water was added. 3. Asteam distillation was performed (internal vapor source) until all the unreacted benzaldehyde (one volume of approximately 75 ml of distillate) separated; then it was discarded. 4. The remaining residue was vacuum filtered to remove resinous solids that have been formed. 5. The filtrate was acidified by slowly adding concentrated HCl. It was cool in an ice bath and the resulting solid was isolate by vacuum filtration. Finally it recrystallized from water to dry, weigh, and determine the yield (estimated yield is 60). Results: Calculations Theoretical yield: Benzaldehyde mC7H6O = 5.0 g C7H6O M = 106.121g/mol C7H6O n = m/MM = 5.0 g / (106.121g/mol) = 0.0147 mol C7H6O is the limiting reagent Cinnamic Acid (C9H8O2) 0.0147 mol C 7 H 6O 1C 9 H 8 O 2 × =0.0147 mol C9H8O2 nC6H10O = 1 1 C 7 H 60 MM = 148.161g/mol C9H8O2 g =¿ 6.89 g C9H8O2 m = n.MM = 0.0147 mol × 148.16 C 6 H 10 O mol Table 1: Yield Product Cinnamic Acid (C9H8O2)

Theoretical Yield 6.89 g

Experimental Yield 2.54 g

% yield 37

Accepted M.P Temperature 133 º C

Experimental M.P Temperature 133 + 2º C

Mass of empty watch glass: 63.22 g Empty watch glass + product + Filter paper: 66.06 g Mass of filter paper = 0.3 g Watch glass + Product = 66.06 g - 0.3 g = 65.76g Mass of product: 65.76– 63.22 = 2.54 g Color of the Product: Mainly White with very few yellow crystalline solids.

Discussion: The synthesis of cinnamic acid in this study was based on the Perkin reaction between benzaldehyde and acetic acid anhydride using anhydrous sodium acetate as the catalyst. Perkin reaction occurs through aldol condensation between benzaldehyde and acetic anhydride in the presence of sodium acetate salt which acts as a catalyst to accelerate the course of the reaction. The Perkin reaction can be seen in Figure 2.

Figure 2: Synthesis of cinnamic acid through Perkin reaction Condensation occured between the carbonyl group of benzaldehyde and the activated methyl group of acetic anhydride. The activation of the methyl group as nucleophilic was carried out by the addition of a basic catalyst. The use of sonochemical methods in organic synthesis offers a shorter reaction time, higher yield, and it’s more environmentally friendly because it minimizes waste and energy use. The compound obtained then was crystallized using cold water to form fine crystals. The synthesized compound obtained has a yield of 37%. Factors that influence the small yield produced were the use of anhydrous sodium acetate catalyst. Aldehydes in the presence of bases produced undesirable side products. From this study, the use of anhydrous sodium acetate as a catalyst can be concluded to be less effective. For future research, it is better to use another acetate salt catalyst, for example potassium acetate. The product was identified to be cinnamic acid because of the white crystalline.The recrystallized sample of product was characterized by its melting point (133 + 2º C). This result of melting was in concordance with that of pure sample and proved that the obtained product may be cinnamic acid. IR spectral analysis of the product was never done for further proof on characterization of the product because of no IR spectrometer. Conclusion: In this research cinnamic acid was able to be synthesized through Perkin reaction using sonochemical methods. Our aim was achieved however it is important to do other tests like Spectroscopic test; IR and NMR to verify the accuracy of the experiments.

POST LAB QUESTIONS 1. Your practical is a condensation reaction of aldehydes and acetic anhydrides followed by hydrolysis that yields cinnamic acid. Draw its reaction mechanism. NOTE: Answer attached at the back 2. Cite the applications of Perkin reactions and the importance of cinnamic acid in industry. Cinnamic acid is used in the manufacture of flavors, dyes and pharmaceuticals; but its major use is for the production of its methyl, ethyl, and benzyl esters. The esters are important component of perfumes. The acid is also precursor to the sweetener aspartame.

Reference: 1. C. I. Chiriac, F. Tanasa, & M. Onciu, “A novel approach in cinnamic acid synthesis: Direct synthesis of cinnamic acids from aromatic aldehydes and aliphatic carboxylic acids in the presence of boron tribromide,” Molecules, vol. 10, no. 2, pp. 481–487, 2005. 2. J. D. Guzman, “Natural cinnamic acids, synthetic derivatives and hybrids with antimicrobial activity,” Molecules, vol. 19, no. 12, 2014. 3. Chemistry LibreTexts, September 13, 2020, Perkin Reaction, MindTouch® and Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot, accessed April 5, 2021, https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Or ganic_Chemistry)/Reactions/Organic_Reactions/Claisen_Condensation/Perkin_Reaction

University of Papua New Guinea 1.30202 Organic Chemistry 1

SCHO Name Max Yeki OL OF ID # 20181070 Practical Room S103 NATU Major Chemistry Chemistry Lecturer Mr Asong Due RAL Date 07/04/ 2021

Practical 3: Synthesis of cinnamic acid through Perkin reaction...