Sabrina Liao
Fig 1. TLC plate of product under UV light
Purpose
The purpose of this experiment is to synthesize isopentyl acetate using the Fischer esterification procedure. Techniques used include: reflux, liquid-liquid extraction, distillation.
Reaction
Mechanism
Table of reactants and reagents
Reactant/ reagent | amount | moles | Molar mass | density | bp/mp | comment |
2-napthol | 1.037g | 0.007 mol | 144.16 g/mol | 1.22g/cm3 | 121-123celcius/285-286 celcius | reactant |
ethanol | 20 ml | 0.334 mol | 46 g/mol | 0.769 g/cm3 | 78.5celcius/ -114 celcius | reagent |
butyl-p-toluenesulfonate | 1.3 ml | 0.00638 mol | 228.3g/mol | 1.12g/cm3 | 172celciu/no m.p | reagant |
Sodium hydroxide | 0.360 g | 0.009mol | 39.997 g/mol | 2.13g/cm3 | 1388celciu/ 318 celcius | reagant |
Mass of empty 100 ml beaker: 50.207 g
25 ml round bottom flask: 28.289 g
Calculations
2-napthol no. of mol: 1.037g/ 144.16 g/mol = 0.007 mol
Ethanol no. of mol: (20ml x 0.769g/ml) / 46 g/mol= 0.334 mol
butyl-p-toluenesulfonate of mol: (1.3ml x 1.12 g/ml) / 228.3 g/mol= 0.00638 mol
Sodium hydroxide no. of mol: 0.360 g/39.997 g/mol=0.009mol
Procedure
1.037 g of 2-napthol was combined with 20 ml of ethanol and 0.36 g of NaOH. The mixture was then placed on the heating mantle and being stirred through the stir plates. 1.30 ml of butyl-p-toluenesulfonate was then added into the mixture. After that, the beginning material mixture and tosylate was spotted on the TLC plate. Then a distilled apparatus was set up and the mixture was distilled for 20 mins. The product was positioned at the 20 minute hashmark on the TLC plate, aligning with the duration of the reaction. Then the reaction was continually progressed for another 20 mins and the product was placed at the 40 minute hasmark. After the distillation apparatus was removed, the product was put inside a 250 ml beaker with cold H2O in it. Then, vacuum filtration was used to purify the product and 10 ml of cold water was used to washed out the remaining product on the wall. Eventually, the MP was measured and it was at 34 celsius degree.
Table of products
products | yield(g) | Yield (mol) | Theoretical yield (g) | Molar mass | Percent yield | Theoretical mp | Experimented MP | density |
I2-butoxynaphthalnene | 0.991 g | 0.0049 mol | 1.40 g | 200.28g/mol | % | 30-33 celcius | 34 celcius | 1.016±0.06 g/cm3 |
Calculation
Yields of I2-butoxynaphthalnene = 0.991 g
I2-butoxynaphthalnene yielded no. of mol: 0.991g/ 200.28 g/mol =0.0049 mol
2-napthol no. of mol= 0.007 mol
Theoretical yield of I2-butoxynaphthalnene: theoretical mass=0.007 mol (same 2-napthol no. of mol=l) x 200.28 g/mol= 1.40 g
Yields of no. of mol= 0.991g/ 200.28 g/mol= 0.0049 mol
Percent yield: %= 0.991 g/1.40 g= 0.71=71%
Discussion
The experiment is an SN2 reaction.
Nucleophile: alkoxide ion arised from 2-naphthol
Electrophile: alkyl group in the butyl tosylate
Leaving group: OTs (tosylate ion)
We can’t use 2-naphthyl tosylate for the reaction because there is an aromatic ring in the substance. The reaction will be hindered because of the benzene ring and there will be no reaction or very little reaction.
The TLC plate of the experiment is as below(Figure 1).Though the TLC result is not so clear, contrast between 20 mins and 40 mins samples suggests the continuous process of the reaction over time. The TLC plate illustrated a faint dot at 20 minutes, an indication the reaction wasn’t completed within the first 20 minutes. A more dense and intense spot shown up at a larger distance on the plate at the 40-minute spot. The size and intensity of the spot was increased compared to the one on the 20-minute mark, illustrating there were more products at 40 minutes. Hence I predict that at 20 mins, the reaction wasn’t completed while it was completed at 40 mins
Rf of starting materials( 2-napthol and butyl tosylate)= 10.4 cm/15 cm = 0.69Rf of tosylate: 11.20 cm/ 15cm = 0.75 Rf product= 11cm/ 15 cm = 0.73
The literature melting point of I2-butoxynaphthalnene is 30-33 celsius and the experimented melting point of our product is 34 celcius. The experimented value is pretty close to the theoretical one hence the obtained product was correct
The IR spectrum of both reactants and products are shown as below (Figure 2 & 3). In Figure 2, the broad OH peak of carboxylic acid at around 3300 cm^-1, which is absent in the figure of the product. Besides, the sharp peak at around 1700-1800ncm^-1 illustrates the c double bond stretch of benzene. Meanwhile, the product figure has a carbonyl stretching of ester within a benzene ring at about 1730^-1while the carbonyl stretching of carboxylc acid is at around 1690 cm^-1.
Reference (all molar mass, density, boiling point/melting are from:)
PubChem. “PubChem.” Nih.gov, National Library of Medicine, 2022, pubchem.ncbi.nlm.nih.gov/.
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