Lab 6

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CHEM 282 Experiment #6: Isolation of Cinnamaldehyde from Cinnamon Sophie Wolkoff (20107258) & Kaelen Partridge (20127197) TA: Bily Deng March 5, 2020 Experimental:

The first step of the procedure involved a simple distillation, performed by each partner, using 0.5 to 0.8 g of sodium chloride, approximately 3 g of ground cinnamon, and 50 to 60 mL of water in a 250-mL round-bottom flask. Approximately 10 to 15 mL of water-cinnamaldehyde distillate was collected by each partner and combined. The distillates were then extracted in a separatory funnel with three successive 5-mL portions of dichloromethane, transferring the dichloromethane layer to an Erlenmeyer flask each time. These layers were dried over sodium sulfate and separated by gravity filtration into a pre-weighed beaker. The solvent was evaporated over a steam bath until an oil remained, then it was cooled and reweighed to calculate the actual weight of cinnamaldehyde. Subsequently, 2 mL of ethyl alcohol was dissolved into the substance. Step two involved the formation of semicarbazone or 2,4-dinitrophenylhydrazone by first adding 1 mL of the cinnamaldehyde-alcohol solution to 0.5 mL of 2M semicarbazide hydrochloride solution in a test tube. Then, 0.5 mL of a base, 2M aqueous sodium acetate solution, was added to the mixture and the test tube was shaken, warmed over a steam bath and left to stand for 15 minutes. The test tube was cooled in an ice bath and the crystals formed were collected by vacuum filtration. Using the dried crystals, the melting point of the substance was determined in order to identify the solid. This step was repeated using 3 to 5 drops of HPLC-grade acetone instead of cinnamaldehyde-alcohol solution, excluding the vacuum filtration and identification step. In the third step, the Tollens’ test was conducted. Approximately 1 mL of 5% silver nitrate solution and 1 drop of 20% sodium hydroxide solution were mixed in a test tube to form the Tollens’ reagent. Between 3 to 6 drops of 15% ammonia solution was added and swirled until precipitate nearly dissolved, then 1 mL of the alcohol solution of

cinnamaldehyde was added to the reagent. The test tube was briefly heated on the steam bath and left to stand for 5 minutes, and any observed changes were recorded. This test was performed again, instead with 2 to 3 drops of HLPC-grade acetone in the place of cinnamaldehyde solution, and observations were recorded and interpreted. Results: Table 1: Cinnamaldehyde Product Mass of cinnamon 3.0 g + 3.0 g = 6.0 g between partners Mass of beaker 51.393 g Mass of beaker with cinnamaldehyde oil 51.464 g Mass of cinnamaldehyde oil 0.071 g Mass of cinnamaldehyde in cinnamon 0.0639 g Percent by weight of cinnamaldehyde in cinnamon 1.065% Mass of cinnamaldehyde oil = Mass of beaker with oil (g) - Mass of beaker (g) = 51.464 g - 51.393 g = 0.071 g Mass of cinnamaldehyde in cinnamon In theory, cinnamon essential oil contains about 90% cinnamaldehyde.¹ = (Mass of cinnamaldehyde oil (g) x 0.9) = 0.071 g x 0.9

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= 0.0639 g Percent by weight of cinnamaldehyde in cinnamon = (Mass of cinnamaldehyde (g) / Mass of cinnamon (g)) x 100% = (0.0639 g / 6.0 g) x 100% = 1.065% Table 2: Melting point analysis Observed melting point Literature melting point of cinnamaldehyde (semicarbazone derivative) Identification of the product 203-210°C 215°C Cinnamaldehyde semicarbazide Table 3: Test Results Test Results Semicarbazide test with cinnamaldehyde - Clumps of white, solid, opaque precipitate formed in a murky white solution within the test tube - A very small yield of white,

opaque, solid flakes were collected after vacuum filtration Semicarbazide test with acetone - White, solid precipitate formed - Produced white crystals in the test tube and white film - Opaque, granulated solid Tollens test with cinnamaldehyde - Immediately after heating, the solution was brown and seemed grainy with precipitate. Some precipitate stuck to the walls - The brown precipitate separated a bit, with the solution around becoming light/more transparent - Dark brown, grainy precipitate sunk to the bottom, with the solution on top being murky brown - Precipitate finally became slightly silvery/black, after about 5 minutes Tollens test with acetone - Solid brown precipitate formed - After heating, the solid separated from within the liquid and moved to the bottom of the tube - A thin black film formed on the surface layer of the liquid - The liquid was transparent and tinted black - Black specks were present in film on the sides of the tube Discussion: Part A Steam distillation is a separation process used to isolate heat-sensitive components within a mixture.³ This method involves separating substances through evaporation and condensation as each component has a different boiling point. Water is a crucial element of the distillation as it forms a mixture with the organic compounds,

lowering their boiling points and reducing their risk of decomposition.³ The combination of water and organic compounds is immiscible, so the organic compounds separate at the top of the liquid. When a mixture of these undissolved liquids are heated, ensuring the surfaces of the liquids are in contact with the atmosphere, the vapour pressure exerted by the system increases because it is the sum of the pressure of all present components.² When this sum of pressure exceeds atmospheric pressure, boiling of the mixture occurs.³ The mixture of steam and organic compounds is extracted by evaporation and separated by filtering out water from the condensed liquid. A semicarbazone is a derivative of semicarbazide that contains an additional functional group of a ketone.⁵ Semicarbazone derivatives are often used for isolation, purification and characterization of aldehydes and ketones due to their highly crystalline and stable structure.⁴ Semicarbazone derivatives form when a nucleophile is added to the carbonyl group. This synthesis occurs via the reaction of aldehydes or ketones with semicarbazide in the presence of acid or base as a catalyst.⁴ The reaction that converts aldehydes and ketones into these imine-like derivatives is exothermic and pH dependent.⁵ The derivatives of 2,4-dinitrophenylhydrazone are formed from condensation reactions involving a nucleophilic attack on a carbonyl group, followed by the elimination of water. Firstly, a methanolic solution of basic 2,4-dinitrophenylhydrazine is mixed with ⁶ an aldehyde or ketone, both of which contain a carbonyl group which provides the electrophile in the reaction. Upon attack, the solution changes colour and forms coloured crystals, doubling this reaction as a test to recognize the carbonyl compounds,

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aldehydes and ketones. After recrystallization of the compound, the melting point can ⁶ be measured and compared to theoretical values to identify the aldehyde or ketone. The Tollens’s test is a common method used to qualitatively distinguish between an aldehyde or ketone within a solution.⁷ This procedure is performed using a colourless and basic liquid called the Tollens’ reagent. This aqueous solution contains silver ions and uses the readily oxidizing ability of aldehydes to form its corresponding carboxylic acid or salt in solution.⁷ Aldehydes have a hydrogen atom attached to their carbonyl carbon which allow rapid oxidation to occur in acidic or alkaline conditions, as opposed to ketones which lack this hydrogen.⁸ When mixed with Tollens’ reagent, ketones will cause no change to the colourless solution. The oxidation of aldehydes that occurs is accompanied by the reduction of silver ions to metallic silver in the reagent.⁷ This produces a grey precipitate of silver or a silver mirror in its container, confirming the presence of aldehyde in the solution.⁸ Part B According to our results from this experiment and their consistency with theory, we determined that we were successful at carrying out this experiment. In part 1 of the experiment, we isolated cinnamaldehyde from cinnamon and collected 0.071 g of cinnamaldehyde oil. According to theory, about 90% of cinnamon essential oil contains cinnamaldehyde.¹ Therefore, we determined our actual yield of cinnamaldehyde to be 0.0639 g and our percent yield in cinnamon to be 1.065%. This was within theoretical range as 6 g of cinnamon can contain 42 to 189 mg of cinnamaldehyde. ⁹ In part 2, the semicarbazide test was performed with both cinnamaldehyde solution and acetone. The cinnamaldehyde sample formed clumps of solid, white

precipitate and the acetone sample similarly produced white solid crystals. Since semicarbazone derivatives were formed from both substances, this proves aldehydes or ketones were present in both samples. Melting point was then determined for the cinnamaldehyde product to identify the substance. Our experimental melting temperature range was from 203°C to 210°C, which is similar to the theoretical melting temperature of 215°C for cinnamaldehyde semicarbazide. Due to this resemblance in experimental findings to theory, we determined this result to be successful. The observations from the Tollens’ test in part 3 from the two samples differed slightly. The mixture of cinnamaldehyde solution with Tollens’ reagent initially formed a dark brown solid which turned silvery-black after 5 minutes, and the HPLC-grade acetone and Tollens’ reagent mixture formed a brown precipitate and a film of black specks. Due to absence of a silver precipitate or silver film in the acetone sample, and the presence of silver in the cinnamaldehyde sample, it was proven that the cinnamaldehyde solution contained aldehydes while the acetone contained ketones. This observation is consistent with theory and the chemical structures. Questions 1. There were multiple sources of error we could have potentially encountered in this lab. One error could have occurred when we were evaporating the solution in order to get the cinnamaldehyde oil product. It is possible that when we did this, we evaporated too much and ended up losing some of our oil product, resulting in a lower yield than what we should have had. Another error could have occurred during the separation with the separatory funnel. While doing this procedure, it is possible that not all of the bottom product was funneled out

during the separation, also resulting in a lower yield than we should have had. Finally, an error we may have encountered during this lab could have occurred due to moving substances from one receptacle to another. In this lab, there was a lot of product movement from vessel to vessel which may have caused error. 2. Steam distillation was used in this lab because of the very high boiling point of cinnamaldehyde. It would be difficult to reach this point using a distillation apparatus if the solution is heated on its own, but by adding water to the cinnamon, the steam was able to form. As a result, this lowered the point at which cinnamaldehyde boiled and decomposed. When it was decomposed, it was able to be carried along with the steam. By increasing the vapour pressure in the apparatus, the steam can decrease the boiling temperature of cinnamaldehyde. 3. Three consecutive extractions with dichloromethane were used in order to isolate the cinnamaldehyde from the water phase. Dichloromethane in particular was utilized because cinnamaldehyde is very soluble within it as it has an aromatic group and, in contrast, it is only slightly soluble in water. To further isolate the cinnamaldehyde from the water, it was dried using sodium sulfate. 4. We were able to identify the cinnamaldehyde using multiple different methods. One method we used was a melting point analysis in which we found the melting point of our crystals and compared them to the literature melting point of a semicarbazone derivative (cinnamaldehyde semicarbazone) and found the points to be very similar, indicating the identity of the crystals. We also used the Tollens’ test as a means to identify our substance. This test is used to indicate the

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presence of an aldehyde in a compound. If an aldehyde is present, a silver layer should appear when the cinnamaldehyde-alcohol mixture was added to the Tollen’s reagent, which is what occurred in this experiment. 5. Semicarbazone Cinnamaldehyde: C 6 H 5 CHCHCHO + H 2 NNHCONH 2 → C 6 H 5 CHCHCH=NNHCONH 2 + H 2 O Acetone: (C H 3 ) 2 CO + H 2 NNHCONH 2 → (C H 3 ) 2 C =NNHCONH 2 + H 2 O Tollens’ Test Cinnamaldehyde: AgNO 3 + NaOH 2 → AgOH + NaNO 3 2 AgOH → Ag 2 O + H 2 O Ag 2 O+ 4 NH 3 + H 2 O→ 2 Ag(NH 3 ) + 2 + 2 OH − C 6 H 5 CHCHCHO + 2 Ag(NH 3 ) 2 + + 3 OH - → 2 Ag + C 6 H 5 CHCHCOO - + 4 NH 3 + 2 H 2 O Acetone: no reaction 6. The semicarbazone test can be used to indicate the original ketone or aldehyde reagent. Semicarbazide hydrochloride will react with the cinnamaldehyde in order to produce cinnamaldehyde semicarbazone crystals, having a characteristic melting point. In contrast, the Tollens’ test is used to differentiate between aldehydes and ketones. The Tollens’ reagent is an oxidizing agent with the ability to oxidize aldehydes into carboxylic acids, however they are not strong enough to do the same with ketones. Ketones are inert to oxidation occurring in the Tollens test because they do not have a hydrogen atom bonded directly to the carbonyl carbon, unlike aldehydes which do have this feature.

References: 1. Cinnamaldehyde. https://pubchem.ncbi.nlm.nih.gov/compound/637511 (accessed Mar 5, 2020). 2. Alo, B. T. Principles of Steam Distillation. https://sciencing.com/principles-steam- distillation-6129502.html (accessed Mar 5, 2020). 3. Helmenstine, A. M. How Does Steam Distillation Work? https://www.thoughtco.com/definition-of-steam-distillation-605690 (accessed Mar 5, 2020). 4. Naimi-Jamal, M. R.; Mokhtari, J.; Dekamin, M. G.; Javanshir, S.; Hamzeali, H. Efficient Synthesis and Deprotection of Semicarbazones under Solvent- Free Conditions. Iran. J. Chem. Chem. Eng. 2012, 31 (1), 1-8. 5. Ahsan, M. J.; Govindasamy, J.; Khalilullah, H.; Nomani, S. Semicarbazone

analogues: A mini review. Der Pharmacia Sinica 2011 , 2 (6), 107-113. 6. Cotton, S. 2,4-Dinitrophenylhydrazine. http://www.chm.bris.ac.uk/motm/dnph/ dnphh.htm (accessed Mar 5, 2020). 7. Gunawardena, G. Tollens' Test. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/ Supplemental_Modules_(Organic_Chemistry)/Aldehydes_and_Ketones/ Reactivity_of_Aldehydes_and_Ketones/Tollens’_Test (accessed Mar 5, 2020). 8. Clark, J. Oxidation of Aldehydes and Ketones. https://www.chemguide.co.uk/organicprops/carbonyls/oxidation.html (accessed Mar 5, 2020). 9. Cinnamaldehyde. http://herbpedia.wikidot.com/cinnamaldehyde (accessed Mar 5, 2020).

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