Oxidation of alcohol PDF

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oxidation of alcohol lab report...

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Abstract Oxidation of alcohol is a common technique to oxidize primary alcohol and secondary alcohol into either aldehyle, carboxylic acid and ketone perspectively. In the lab, it focused on the mechanism turning one function group into different functional group. Using extraction of solvents, it sepeated the target compound, cyclohexanone, which also the final product. Extraction uses concept of imissible of solvents in the mixture. In this particular extraction, it used cyclohexanone and water. Then it is confirm the identity through IR spectra. It shows the conpound has C-H bonds and C=O.

Oxidation of alcohol Introduction Oxidation of alcohols is a reaction can yield to different product depends on order of alcohol in the compound. primary alcohol reaction after being oxidized forming aldehydes and carboxylic acids. While secondary alcohol will oxide into ketones (Lab manual, 2018). Both primary and secondary alcohols, there are two Hydrogen atoms will be removed from the alcohol groups and returns back to C-O bond. It will form a double bond between C=O after releasing another attached group like -H (figure 1). Tertiary alcohol cannot be oxidized because the C bonds to -OH group does not have extra -H atom, instead it bonds with others Carbon and the -OH group (figure 1). It does not have enough of space to form any kind of C=O.

Figure 1. Primary, secondary and tertiary alcohol is oxidized into the products.

In the process of oxidation of alcohol, it needs an acid to carry the reaction. Hypochlorous acid is a product of sodium hypochlorite and acetic acid. Through this acid, a focus reagent cyclohexanol will be oxidize into cyclohexanone. Sodium hypochlorite (NaOCl) is an anhydrous compound. It can be use as disinfectant for household works and modified into wound cleaning. (Practical Organic Chemistry, 2009). When combining it with carboxylic acid, it is going to be acetic acid in this lab, it yields to hypochlorous acid solvent (HOCl). NaOCl + CH3COOH  HOCl + CH3COO- Na+ When secondaty alcohol in cyclohexanol is intereacting with hypochlorous acid, the positive charge of Cl- attracts the partial negative charge of O- in -OH group in respect of Oxygen charge is more negative than the Cl. After get attack from O:, Cl breaks the bond with hydroxide group in hypo chlorous acid (-OH). Since -Cl attaches with -OH on cyclohexane, the O atom becomes more positive compares with H+ atom. The hydroxide in the environment will attack the more postivie H+, breaks the bond between O-H and returns the electron back to O. At this moment, O-Cl is good leaving group and there is more OH- concentrated in the solvent. Therefore, OH- will attach to H+ in C supporting O-Cl because O- is slightly negative than C. The electron will transfer and form a C=O, a carbonyl group, Cl- will cleave the bond itself. In the end, the product is cyclohexanone, a Cl- and 2 H2O.

Figure 3. Mechanism of cyclohexanol oxidation into cyclohexanone. However, the product cyclohexanone will go through the extraction from aqueous solution. The extraction is a techinique to purify and separate organiic compounds through isolation of organic chemincal reaction (MASHSH, 2010). It is a common techinique, even using in extract caffein to decafferin coffee, or making vanilla extract. The concept of extrasound surrounds the imisscle of liquids, the first solvent ix missed with an insoluble second solvent. When it is a liquid-liquid solution, the more soluable is going to be the solvent. In most of the case, one of solvent is water, the extraction carrying out the last polar organic solvent from water attraction. It is not able to extract something miscible/soluble with water that leads into one layer (MASHSH, 2010). Characterization of product after extraction will be performed by IR and 2,4dinitrophenylhydeazine chemical test (2,4-HNPH) or Brady’s reagnent. In IR spectroscopy, it uses to identify the cheminal functional group in compound. Each functional group has its infrared region that reflect the vibration of molecule. Since molecules bonded together or having similar characteristic will reflect same vibration or wavenumber region (MASHSH, 2014). And 2-4 HNPH chemical test will show positive results for aldehydes and ketones. It is a simple test using dinitrophynulhydrazine reagent and ethanol and target reganent. The positive test will turn from orange like yellow-orange precipitate, it confirms the C=O , carbonyl group in an aldehyde or ketone (Organic Syntheses, 1943). Methods and materials.

Preparing mixture. 10 mmoles of Cyclohexanol was placed in 50-mL Erlenmeyer flask with a stir bar. Carefully added 2.5 mL of acetic acid. In separatory funny, prepared 15 mL of bleach (~5.25% sodium hypochlorite solution) over Erlenmeyer flash, then added the bleach dropwise into cyclohexanol and acetic acid mixture flask. Prepared an ice-batch if reaction flash gets hot after adding bleach. Obtained a sample of new mixture from reaction flask by stirring rod. Prepared a wet of starch0iodide test paper with deionized water then placed the sample into the wet part. If there was excessive of hypochlorite, the paper would turn dark purple color. Added more bleach in small increments ( 0.5-1.0mL) until the test became positive. The complete look after addition of bleach would be pale yellow to yellow-green mixture. The mixture was test positive for excess hypochlorous acid. But it still needed to be sir for extra 15 minutes. Then performed the test again for excess hypochlorous acid. Added a spatula-tip full of solid sodium bisulfite (NaHSO3), stirred and tests for presence of hypochlorite. If it was positive, then keep adding NaHSO3 until it became negative test for presence of hypochlorite. In the reaction mixture, added 2 drops of thymol blue indicator then 6Mk NaOH dropwise until solution became basic (color light blue). Then it should keep adding solid NaCl until solution was saturated with salt. Discarded the liquid mixture into separatory funnel. Extraction and Venting. Added 5 ml of methylene chloride into the separatory funnel. Released the pressure from the top after capping and before mixing and venting. It was important to vent throughout

the mixing process. In beginning of mixing, placed a stopper on the top of separatory funnel and inverted with stopcock. Once ready, after vented, mixed the solution by holding stopper in place and shake the separatory funnel and released the pressure, kept doing until the mixture is thoroughly mixed. Set up the separatory funnel with ring stand, let the layers be separated without cap on the tube. Collected the organic layer then extracted the aqueous layer again by same techniques and addition of 5mL of methylene chloride. Characterization Dried all organic layers with anhydrous sodium sulfate. Added a boiling stick in the flask and evaporate the solvemen over hot plate. Recorded for yield of ketone. Recorded IR spectra. Result Starting material of cyclohexanol: 1.0 mL

1.0 mL x 1kg/cm3 x 0.001g/kg x 10 mmol x 1mol/0.001mmol x 100.158g/1mol = 1.00158g = 1.0g Final mass of final product: 0.562 g

Percent yield = ( actual yield ) / ( theoretical yield ) x 100% = ( 0.562 g / 1.0 g ) x 100% = 56.2%

Figure 4. IR spectra of final product, cyclohexanone.

Discussion Oxidation of alcohol is a chemical mechanism turning alcohol group until a carbonyl group. In this experiment, it turned a secondary alcohol in cyclohexanol into cyclohexanone, which presents a ketone group. The experiment also used technique of extraction for purification and separate the product from aqueous environment, that H2O as byproducts of reaction. The percentage yield was 56.2 % from the original mixture and able to recover the purified cyclohexanol. Using IR spectrometry, it suggested the identity of new product cyclohexanone by grouping the functional group. At peak 2938.72 cm-1 and 2863.57cm-1, it confirmed there are CH groups. Then at peak 1711.35 cm-1, it showed there was a carbonyl group, C=O. Therefore, the experiment was successfully obtained cyclohexanone using cyclohezanol oxided into a ketone.

Preferences Mohrig, J. R., Hammond, C. N., & Schatz, P. F. (2014). Techniques in organic chemistry miniscale, standard taper microscale, and Williamson microscale. New York, NY: Freeman....