Syntesis of Acetanilide

 

PREPARATION ACÉTANILIDE  Jonathan R. Cuellar 20131150034  Juan Camilo Figueroa Galindo Galindo 20142150081 20142150081  Juan Sebastián Sebastián Romero 20141150077  Francisco Jose de Caldas Caldas University University  Faculty of Science and Education, Education, Degree Degree in Chemistry Chemistry

1. SUMMARY: This practice was made with the purpose to synthesize of phenylacetamide or acetanilide was by acetylation method; the synthesis synthes is was carried out in the middle of acetic acid, which acted as a catalyst for the reaction between the acetic anhydride and aniline, synthesis took place through a Nucleophilic addition mechanism. Amide formation occurred in a series of important steps (effect of acid medium,  Nucleophilic  Nucleophi lic attack, deprotonation) deprotonation) by this reason it was essential essential to maintain the conditions of acidity, temperature (atmosphere and ice bath), agitation, elimination and reflux (10 minutes); finally retrieved compound is recrysallisation and determined the melting point as a criterion for purity, yielding value ofto (85°C and 105°C) and with recrystallisation and an infrared analysis aallowed corroborate his without most important bands, possiblyrespectively indicating ,their respective synthesis.

Keywords: nucleophile, electrophile, amines, amides.

1. INTRODUCTION: Amines are organic ammonia derivatives Considered to alcohols and ethers similarly Considered are organic derivatives of water, amines Having a nitrogen atom With an electron pair unbound, This causes the basic and nucleophilic amines be. Most of the chemistry of the amine depends on the unbound electron pair.(McMurry, 2008)

Amines are widely found in nature, mainly in living organisms, tissues Such as animals, nicotine and cocaine are examples of snuff amines, amino acids are the additional structural basis of all proteins.(McMurry, 2008)

 Fig. 1. Structure Structure of nicotine. nicotine.

Secondary and tertiary amines May be alkylated by primary reaction with an alkyl halide primary, these reactions are difficult to check and give Mixtures of products usually, unlike tertiary amines are rented to give quaternary ammonium salts. Primary and secondary amines can be acylated by a Also nucleophilic substitution reaction in the acyl group With an acid chloride or an acid anhydride to produce an amide. (McMurry, 2008)

 

   Fig. 2. Reaction of Obtaining an amide, in a common case esta drug acetaminophen.

2. METHODOLOGY:  Reduction of nitrobenzene. nitrobenzene. It took 30 mmoles of nitrobenzene and 65 mmoles of mossy tin in a 250 mL round  bottom flask, securely clamped clamped above a stir motor. Place a Claisen adaptor on top of the flask; put a water-cooled condenser on one outlet of the Claisen and a separatory funnel on the other. Add a spin bar to the flask and

add 18 mL of 50% NaOH through the Claisen adaptor. This reaction is exothermic, so have a cool water bath (not an ice bath) ready in case the flask gets too warm. The mixture must be strongly alkaline to ensure complete liberation of the aniline .Dilute the reaction mixture with 40 mL of water and then steam the heat source. sour ce. Collect the distillate in a 100 mL graduated cylinder: the first 18 mL or so of distillate should be quite cloudy because you are distilling over a mixture of aniline and water. Once the distillate ceases to be turbid, collect an additional 4 mL. Transfer the entire volume of distillate to an Erlenmeyer (do not stopper the flask until the solution is cool!) and save for use in the acetylation step. Place the pot residue in the Aqueous Waste carboy in the main hood.  Preparation of acetanilide. acetanilide.

turn on the stir motor. Place 15 mL of concentrated HCl in the separatory funnel. Add the HCl to the nitrobenzene/tin mixture a few mLs at a time. After each addition, monitor the flask so that it does not get too hot; if necessary, immerse the reaction flask briefly in a cold water bath. After the initial reaction has subsided, add another portion of the acid. Again, control the temperature of the reaction in a cold water bath. Continue until all of the HCl has been added. After all of the acid has  been added let the mixture stir at room temperature for about 10 min. Remove the

Dilute the distillate from the previous previo us step with water to a volume of 65 ml final. Add a spin  bar and place it over a stir stir motor. Add 2 mL of Concentrated hydrochloric 5 acid and stir to homogeneous solution obtener. Dissolve 4, 5 g of sodium acetate trihydrate in 10 mL of water in a beaker. Measure 3, 5 mL of acetic anhydride into a graduated cylinder. Warm the solution of aniline / hydrochloric hydrochloric acid to 50˚C on a steam bath, add the acetic anhydride, stir, and add the sodium acetate then a solution all at once With stirring. Remove the heat source; Should a white solid begin to precipitate.

separatory funnel (and rinse it) and place a ground glass stopper on the open Claisen outlet (the other outlet still has the watercooled condenser). Place a heating mantle under the reaction mixture and heat and stir for 20 min. Test to see if the reaction has gone to completion by testing for unreacted nitrobenzene (below). If nitrobenzene remains, heat and stir for an additional 10 min and test again. Test for unreacted nitrobenzene: Put a few drops of the reaction mixture in a small amount of water in a test tube; a clear solution (no oily drops) indicates

Continue to stir the mixture for 20 min Then cool it in an ice bath to complete crystallization. Isolate the product by suction filtration, wash it with cold water, and allow it to dry.

that there is no nitrobenzene present. When the reaction is complete, cool the reaction flask to room temperature. While stirring, carefully

Table 1. Data Obtained in the synthesis. synthesis.

3. RESULTS AND ANALYSIS:

Melting point before recrystallizing Melting point after recrystallization

85 ° C 108 ° C

 

The reduction of the nitrobenzene can occur by several mechanisms, hydrochloric acid and iron is used, this reaction happens while the necessary hydrogen comes from the water and the iron passes to Fe3O4-, when the reaction is finished it is necessary to neutralize and remove the aniline so that it does not A second

In the second step the electron pair of the nitrogen attacks the carbon positively charged and binds to this, then the electron of oxygen regenerates the carbon double bond and releases the link with the other oxygen stabilized acetate ion form. (McMurry, 2008)

 product is obtained. It is important that whenever aniline is synthesized by reduction of nitrobenzene a neutralization is carried out, and that the reaction can undergo condition and different products, in addition the aniline can react with the medium and give new  products. The reduction reaction can also be given by using tin, which with the nitrobenzene in acid medium, give the amine product as a hydrochloride. This reaction occurs by catalytic hydrogenation of the nitro group, or reduction thereof. In this reduction the tin state (0) is oxidized to tin (IV) and the nitrogen is reduced, the tin (II) chloride likewise reduces a nitro group, and in the end the amine is found as hydrochloride, which in Presence of a strong base, releases the aniline. (McMurry, 2008)

 Fig. 5. Attack positively positively charged nitrogen carbon.

 Fig. 6. Formation of the double bond with oxygen and breaking the link with the other oxygen. After that the acetate ion attacks one of the hydrogen’s bonded hydrogen’s  bonded to nitrogen is breaking the link and thus recovering its nitrogen electron  pair and forming the acetic acid as a  byproduct.

 Fig. 3. Reaction Reaction to obtain obtain aniline. aniline. The reaction mechanism for obtaining acetanilide is given first by the formation of a negative charge on one of the oxygens with double bond anhydride resonance breaks the double bond and thus the carbon becomes  positively charged as follows:

 Fig. 7. Acetate attack one of the hydrogen’s hydrogen’s of  of nitrogen.

 Fig. 8. Formation of acetanilide acetanilide and acetic acid.  Fig. 4. Breaking Breaking of the pi link by resona resonance. nce.

 

The melting point before recrystallization was 85 ° C, quite apart from pure acetanilide acetanilid e which is 114 ° C, thus in a first step can be said that the obtained crystals had a considerable amount of impurities, this supported the color crystals taking as an additional factor as these had a light yellow-green what we could indicate the presence of aniline, after making the re crystallization from hexane cycle melting point was 108 ° C which indicates that much of the impurities have been removed and the crystals obtained white have a high purity level. Then the IR spectrum found in databases is  presented:

 Fig. 9. IR spectrum spectrum consulted consulted for aniline. In the spectrum can be observed two bands of high intensity between 3300 and 3400 indicating the presence of primary amine, a  band of medium intensity above 3000 indicates sp2 hybridized, a doublet at l600 indicating the C = C band of 1500 high intensity indicating tension CH and finally a set of bands below 1000 indicating a mono substitution on the benzene ring.

4. CONCLUSIONS: -   Fig. 8. IR spectrum consulted consulted acetanilide. acetanilide.

Synthesis was achieved an amide from an amine and an anhydride by nucleophilic addition mechanism. Reflux keeps the temperature conditions in the reaction volume and to ensure that the two contact substances react in as much as

The band in the region 3294 cm-1 indicates the voltages N- H of an amino group, the band in the region of 1665 cm-1 indicates the presence of the carbonyl group, in the region of 1436

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cm-1se has a characteristic band CH3 voltage of the band of 754 cm-1 indicates a mono substitution, the band 1324 cm-1 corresponds to the voltage CH3. According to the molecular formula, it acetanilide like structure that complies with the characteristics characteristi cs that casts the infrared spectrum is proposed.

 possible. The IR spectrum is a very useful tool that allows us to corroborate the compound obtained in addition to the tests such as boiling or melting point that are used as purity criteria. -  The re-crystallization allows the impurities that are soluble to be removed from the compound therefore it turns out to be a quite useful method to purify solid compounds. - 

 

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ibliography

McMurry, J. (2008). Química Orgánica . Belmont: Cengage Learning . Morrison, B. (1987). Quimica organica . Boston : Pearson .