LAB REPORT 7 Aldol Reaction Synthesis 1 5 Diphenyl 1 4 Pentadien 3 One

Rodney Pujada Jessica Brizuela LAB REPORT No 7: The Aldol Reaction Synthesis, purification and NMR Analyiss of 1,5-diphenyl-1,4-pentadien-3-one.

Date: December 8th, 2016 I. PURPOSE: The purpose of this week’s lab was to conduct an Aldol condensation reaction. This particular reaction involves the joining of acetone and benzaldehyde molecules and the loss of water. This reaction is a base-catalyzed reaction that involves a carbanion intermediate. The carbanion is known as an “enolate anion” in which the hydrogens on the alpha carbon are unusually acidic. II. INTRODUCTION: Dibenzalacetone, also known as dibenzylideneacetone or DBA, is often utilized as an ingredient in sunscreen lotions and sprays because it has spectral properties that make it capable of absorbing UV light. It is also known to possess antiinflammatory properties and can therefore be used to treat pain, swelling and inflammation. Dibenzalacetone canal so be used as a ligand in organometallic chemistry, and its derivatives are often utilized as polymer cross linkers. Most importantly, the synthesis of dibenzalacetone via the aldolcondensation of benzaldehyde and acetone is an extremely effective. In this experiment, we carried out an aldol condensation reaction in strongly basic conditions with benzaldehyde acting as the electrophile and acetone forming the enolation. This reaction synthesized dibenzalacetone with a fair yield of 73.03%. Our mechanism is the following table No 1:

Table No 2: compound specific characteristic. Benzaldeh yde

Acetone C3H6O

C7H6O

Sodium Hydroxi de

Ethanol C2H6O

Dibenzalacetone/ Dibenzylideneacetone C17H14O

NaOH

Molar Mass (g/mol)

106.12

58.08

39.9971

46.07

234.292

BP (°C)

178.1

57

1,388

78.37

130

MP(°C)

−57.12

−93

318

−114

112

Density (g/ml)

1.044

0.791

2.13

0.789

1.1

Solubility

In ammonia

In water

Polar solvents

Polar solvents

Soluble in nonpolar solvents

Refractive Index (nD)

1.545

1.359

1.357

1.361

1.649

III. RESULT AND CALCULATIONS 3.1 DATA Compound use to the experiment in grams 0.012 moles of Acetone * 58.08 g/mol = 0.697 g of Acetone 0.024 moles of benzaldehyde *106g/mol = 2.456 g of benzaldehyde.

3.1.1. Mass of crude product = 1.6070 g CONVERT TEORIC PRODUCTION IN GRAMS 2 mole of benzaldehyde = 2mole*(106g/mol) = 212 g of benzaldehyde 1 mole produced of dibenzalacetone = 1mol*234.29 g/mol = 234.29 g of dibenzalacetone We use 2.456 g of benzaldehyde = 2.456 g III.1.2. By balance equations calculate the weight in grams of dibenzalacetone

= 2.456 g of benzaldehyde* (234.29 g of dibenzalacetone/212g of benzaldehyde) =2.71 g of dibenzalacetone Weight theorycal of dibenzalacetone = 2.71 g Weight practical of dibenzalacetone = 1.6070 g III.1.3. Percentage Yields of dibenzalacetone Weight theorycal of dibenzalacetone = 2.71 g Weight practical of dibenzalacetone = 1.6070 g Percentage Yield = (weight of crude *100)/ weight of theorycal product. Percentage Yield = 1.6070 g*100/2.71 = 59 % Percentage Yield of benzalacetone = 59 % Our Sample recovered after column chromatographic of crude product Weight after Column Chromatographic dibenzalacetone = 0.32 g III.1.4.

Measuring melting point of crude product

Melting point of dibenzalacetone = 109.2 ºC in the range of 88-113 ºC Melting point of dibenzalacetone after column chromatographic = 110 ºC in the ramp of 88-123 ºC

III.2. COLUMN CHROMATOGRAPHIC AND NMR GRAPHS Graph No 1 : Column Chromatographic taken before and after purificaion

For the experimental production we obtain Rf for SM = 1 cm Rf for CO = 1.71 cm Rf for CP = 3.7 cm For the purified product by column chromatographic we obtain Rf for CO = 2.7cm Rf for PP = 2.7 cm

Graph No2 and 3 : Our represented NMR for our product are the following.

IV. DISCUSSION For our experiment we synthesized dibenzalacetone by 59 % of yield recuperation. We have a complete reaction because in our TLC is clear and define spots that showed by TLC. Rf = 3.7 in our experiment, and in our final purified product was Rf = 2.7 after the column chromatographic. Also, our melting point showed a m.p. before purification is 109.2ºC and m.p. after purification of 110 ºC. By graph No 2 we calculate the coupling constant calculation for two hydrogens present in the compound JHa = (7.116-7.076)*400 = 16Hz and JHb = (7.769-7.729)*400 = 16 Hz. Geometric isomerism refers to the cis/trans orientation of alkenes within a molecule. There are two alkenes and both can be either cis or trans. The orientation of two protons on a disubstituted alkene uses their coupling constant. Generally cis protons will have a smaller coupling constant between 7 to 12 Hz and trans protons will have a larger coupling constant between 13 to 18 Hz. The two wide doublets in the NMR correspond to the protons adjacent to the carbonyl on the alkenes because the peak are defined as neighbors alkenes; therefore there is a trans trans configuration. V. CONLUSION For our experiment calculation, we concluded we had a 59 % of yield for dibenzalacetone with a constant melting point before and after the purification by the column chromatographic. Also, we observe in our mechanism of reaction, -OH is known to yield the enolate, which we must generate from acetone, in small amounts. So we must add more than a 1:1 ratio of acetone and sodium hydroxide in order to generate more enolate. Therefore, we had to measure a exactly amount of compound benzaldehyde and acetone to get a good results. Also, we obtained a trans trans isomer because our coupling constant are higher. The trans isomer will show doublets with a higher coupling constant. VI. REFERENCES 1. ANALYTICAL CHEMISTRY FOR TECHNICIANS. Third Edition. Lewis Publishers.2003. Pages 337-341 2. Laboratory Techniques in Organic Chemistry. Morhig and others. 1 st. Edition .W. H. Freeman and Company. 2014. Pag: 142-152 3. Table 12.1 page 425 “Characteristic IR Absorptions of Some Functional Groups” 4. McMurry, John. "Organic Chemistry." Sandra Kiselica. Belmont, CA:Brooks/Cole, a division of Thomson Learning Inc., 2008. Abstract: brief statement of the results - product name, yield, mp, how it was synthesized and purified

Intro- method and reaction scheme (+MW of each reactant), mechanism Results: how much of the SM was taken, theoretical yield calculations; mass of crude %yield; mp of crude, of purified, % recovery (must know how much you took for the purification and how much you isolated after the column - put in in the table) TLC data (both plates - see the files posted in the last week block). For details, consult the syllabus. Attach NMR spectrum given in the lab or download it (posted in the last week block) with all protons labeled on the structure and on the spectrum. If you need a hard copy - come to my office. Discussion 1. reaction progress - complete/incomplete based on TLC 2. Purity of your product based on TLC and mp (must compare experimental values to the lit value). 3. Yields and recovery% - account for errors and losses of the product 4. Decide whether the product is trans-trans, cis-trans or cis-cis based on NMR and mp. formula for coupling constant calculation: J = 10^6*(difference in chemical shift/400) Conclusion: Asses overall performance for this experiment and tell what you have learned from it. Post-lab questions (extra credit - 6 pts): 1. During the column chromatography why was it important to load the concentrated solution of the sample? 2. Why you shall never let the column run dry? 3. How can you use NMR and IR spectroscopy to monitor the progress of the reaction you performed? Hint: think what peak will disappear and what will appear when reaction is done. Should you have any question - please see me