Preparation of Acetanilide

Formula:

• Mole Ratio:
  • moles = mass ÷ Rmm
  • Moles Calculator: https://www.omnicalculator.com/chemistry/mole
• Limiting Reagent:
  • The reactant that limits the amount of product produced is known as the limiting reagent.
  • Steps to calculate the limiting reagent:
    • Determine the balanced chemical equation for the chemical reaction.
    • Convert the given information into moles (most likely, through the use of molar mass as a conversion factor).
    • Examine the estimated mole ratio against the actual mole ratio. The actual mole ratio would be regarded the reaction equation's coefficient (moles). The limiting reagent is the reactant that creates the least quantity of product, whereas the excess reagent is the reactant that produces the most amount of product.
    • To find the amount of remaining excess reactant, subtract the mass of excess reagent consumed from the total mass of excess reagent given.
  • Limiting Reagent Calculator
• Theoretical yield:
  • theoretical yield = rmm of product * (moles of limiting reagent in reaction * stoichiometry of product)
  • Theoretical Yield Calculator
• Percentage yield:
  • percent yield = (actual yield (mass of product obtained during experiment)/ theoretical yield) * 100
  • Percent Yield Calculator

Pre Lab Notes:

• Reaction Structure: Aniline + Acetic Anhydride + HCl (aq) + Sodium Acetate = Acetanilide + Acetic Acid
• Videos:
  • Introduction and Reaction for Preparation of Acetanilide
  • How to Flute a Filter Paper
  • Isolating a Solid using Vacuum Filtration
  • How to use a melting block to determine the melting point of a compound
• Safety Data Sheet of Acetic Anhydride
• By using the safety data sheet, it can be determined that acetic anhydride causes skin burns and eye damage, is toxic if inhaled, flammable but a weak oxidizing agent (not a strong one).
• Aniline is sometimes coloured because it undergoes oxidation in the bottle over time.
• Another name for an Erlenmeyer flask is a conical flask.
• Fluting the filter paper is often when carrying out a gravity filtration because it speeds up the filtration rate.
• Buchner funnels don't come in the same standard size, they have diameters ranging from 10.25 inches to 36 inches.
• Rubber cones are used in vacuum filtration to create a seal and trap impurities but it doesn't prevent the apparatus from breaking.
• The sodium acetate solution is added immediately after addition of acetic anhydride.
• Some of the holes in the porous plate of the Buchner funnel should remain uncovered by the filter paper to speed up filtration.
• The plateau temperature should be 10 degrees lower than the expected melting point set on the machine.
• To get the temperature back down to the plateau temperature on the machine, use the plateau set button.

Lab Notes:

• IR Spectra of Aniline
• IR Spectra of Acetanilide
• The aim of this experiment was to synthesize acetanilide from aniline via a nucleophilic acyl substitution reaction.
• Experimental Procedure:
  • Sodium acetate was measured and dissolved with water in a beaker for later use.
  • Hydrochloric acid was combined with water in an Erlenmeyer flask before aniline was added beneath the fume hood. 
  • A 1/4 full spatual of decolorizing charcoal was combined, then the solution was filtered out using fluted filter paper into a second Erlenmeyer flask, and the anilinium chloride combination was heated to 50 °C on a laboratory hot plate. 
  • Under the fume hood, acetic anhydride is added to the flask once again, and the previously prepared aqueous sodium acetate is immediately poured in.
  • The flask was swirled several times before being placed in an ice bath for 20 minutes. 
  • When the amide crystals form after cooling, they are filtered using vacuum filtration and rinsed with cold water to eliminate contaminants. 
  • When the crystals have completely dried, they are patted dry with a filter appaper to eliminate any remaining water.
• The addition of decolorizing charcoal to the aniline-HCl mixture is intended to eliminate the coloured, impure chemicals present in the solution by adsorption. When colored chemicals pass adjacent to one of the charcoal's numerous bonding sites, they are attracted by the carbon surface and become locked there. When all of the bonding sites in the decolorizing charcoal molecules are filled, the decolorizing charcoal stops operating.
• Reaction between aniline and HCl: Aniline + HCl = Anilinium Chloride
• Anilinium chloride salt is more soluble than aniline because it is a polar molecule due to the aromatic ring and positive charge from the ammonium ion, making it polar and allowing it to dissolve easily in solutions with similar polarities (i.e. water). Another reason is that aniline is only marginally soluble in water due to its bulky, hydrophobic phenyl group, thus any hydrogen bonding with water is insignificant.
• Reaction of acetoxy ions from sodium acetate and anilinium chloride to give aniline and ethanoic acid: Anilinium Chloride + Acetoxy Ion = Aniline + Acetic Acid
• Reaction mechanism of acetoxy ions from sodium acetate and anilinium chloride to give aniline and ethanoic acid
• As aniline and ethanoic acid (products) have lower energy than anilinium chloride and acetoxy ion, the equilibrium completely shifts to the right. When compared to the acetoxy ion, ethanoic acid is a more stable molecule due to the presence of non-equivalent contributing structures, hence the equilibrium shifts to the right.
• Reaction mechanism of aniline and acetic anhydride 
• The goal of the experiment was to create acetanilide from aniline via a nucleophilic acyl substitution process. 
• The product formed was purified by recrystallization, followed by different tests (nitric acid test, IR spectroscopy melting point data) to establish that it was acetanilide. 
• The reasons for a lower yield might be due to contaminants that remained after the procedure, using too much solvent meaning more acetanilide would stay in solution, or product loss during transfer.
• The theoretical melting point of acetanilide is 114.3 °C.
• The melting range of pure acetanilide is 113 - 115 °C.
• As it takes a modest amount of energy to melt the pure solids in it, impure compounds frequently begin to melt at a much lower temperature or across a larger temperature range.
• Recrystallization is a process that works well for solids with few impurities, which was ideal for purifying the acetanilide.