Adipic acid from cyclohexanone

• By Dr. Robert D. Craig, Ph.D.

Message from stockroom

• KMnO4- vessels easily explode-oxidizing agents support combustion

• The vessels will become hot at the bottom and splatter

• *bad incident 2 semesters ago

THIS IS EXPLOSIVE!!!!

PLEASE BE CAREFULL!!!!

• Safety Features:

1. Add concentrated hydrochloric acid to the strongly basic solutionvery cautiously (or erupting may occur). Wash the affected area thoroughly with cold water if acid is spilled on the skin.

2. Handle potassium permanganate carefully. It is a strong oxidising agent. Avoid contact with skin and eyes.

3. Avoid breathing vapours of cyclohexene and methanol

Abstract:

• In this experiment, adipic acid was synthesized from cyclohexanone and concentrated nitric acid. The HNO3 and cyclohexanone were combined very slowly, since the reaction is very exothermic. Once the reaction was complete, the product was allowed to crystallize and the solvent was removed.

Abstract

• The adipic acid crystals were then washed with a small amount of water, dried for a couple days and weighed.

THIS IS EXPLOSIVE!!!!

From website• EXP. 8: Elimination Reaction E1: Cyclohexene from cyclohexanol

(fractional distillation)• EXP. 8: IR spectra of cyclohexanol and cyclohexene• EXP. 8: IR and NMR Handout• EXP. 8: Post Lab• EXP. 9: Elimination Reaction E2: Cyclohexene from

bromocyclohexane• EXP. 9: Reflux Apparatus (You may bring this handout to lab!)• EXP. 9: Distillation Apparatus (You may bring this handout to lab!)

and Actual Photo• EXP. 9: IR and NMR Handout• EXP. 9: Post Lab

The percent yield of this experiment

• The percent yield of this experiment was 62.33%. This was low because when a Pasteur pipet was used to remove the solvent from the reaction tube, many crystals were lost. In addition, some crystals remained in the reaction tube as well as on the boiling chip and were not available for weighing. The observed melting point of the product was 148 - 151°C. This was a little lower than the literature value of 153°C, which may have been due to the fact that not all the solvent or water evaporated from the crystals. An infrared spectrum of the product confirmed its identity as adipic acid and indicated that the reaction was successful.

The observed melting point

• The observed melting point of the product was 148 - 151°C. This was a little lower than the literature value of 153°C, which may have been due to the fact that not all the solvent or water evaporated from the crystals. An infrared spectrum of the product confirmed its identity as adipic acid and indicated that the reaction was successful.

Introduction

• The purpose of this experiment is to synthesize adipic acid from cyclohexanone and concentrated nitric acid via an oxidation reaction. The cyclohexanone is oxidized using nitric acid and thus forms adipic acid. Melting point and infrared spectroscopy will be used to characterize the product.

Materials Used:

• Sand bath Rubber bulb • 2, 10 x 100 mm reaction tubes Erlenmeyer

flask, 25-mL • Boiling chips watch glass • Pasteur pipettes clamp • Glass stirring rod ice for ice bath

Experiment 12 Preparation of adipic acid from cyclohexene.

•

In this laboratory period the cyclohexene prepared in the previous experiment is oxidised to adipic acid. The procedure is written for a specific amount of cyclohexene. Before coming to the laboratory calculate the amounts of reagents required for the amount of cyclohexene you have available.

Experiment 12 Preparation of adipic acid from cyclohexene.

• Theory:

The cleavage of double bonds by oxidation is useful in the synthesis of acids and ketones and determining structures. Several methods are available including ozonolysis and hot concentrated permanganate. The products obtained depend on the original structure of the olefin. The equations below illustrate the products from cleavage of alkenes:

Experiment 12 Preparation of adipic acid from cyclohexene.

Experiment 12 Preparation of adipic acid from cyclohexene.

• The balanced equation for the oxidation of cyclohexene with permanganate is shown:

Technical Points

•

Vacuum Drying of Organic Solids Organic solids may be dried by allowing air to pass through the filtering apparatus for a few minutes. This, however, only works well when the solvent used for crystallization has a low boiling point. A very effective method of rapidly drying materials isolated from high boiling

Technical Points

• liquids is to heat them under vacuum. A simple way of carrying out such an operation on a small quantity of material involves using a side arm test tube. The material to be dried is placed in the bottom of such a tube, which is then stoppered with a cork. The side arm is connected to the water aspirator.

always DISCONNECT the hose

• The vacuum is turned on and the test tube is heated gently in the steam bath. The test tube is shaken regularly until the solid looks dry and no longer sticks to the walls of the tube. Remember to always DISCONNECT the hose from the test tube before turning off the water!

always DISCONNECT the hose

• Remember to always DISCONNECT the hose from the test tube before turning off the water!

• Safety Features:

1. Add concentrated hydrochloric acid to the strongly basic solutionvery cautiously (or erupting may occur). Wash the affected area thoroughly with cold water if acid is spilled on the skin.

2. Handle potassium permanganate carefully. It is a strong oxidising agent. Avoid contact with skin and eyes.

3. Avoid breathing vapours of cyclohexene and methanol

concentrated hydrochloric acid

Procedure:

• Procedure:

To a 250 mL Erlenmeyer flask, add water (50 mL), cyclohexene (2 mL, density = 0.81 g cm-3), and potassium permanganate (8.4 g). Stopper the flask loosely, wrap with a towel and swirl vigorously for 5 minutes. The flask should feel warm.(If no rise in temperature is detected, remove the stopper, warm the mixture on the steam bath and loosely replace the stopper). Swirl the flask at frequent intervals for 20 minutes (your yield depends on how well you mix the reactants at this stage).

THE BOTTOM WILL GET HOT!!!

IT CAN EXPLODE!!!

• The temperature of the mixture should be between 35° and 40°.

•If the temperature rises above 45°, briefly cool in an ice-water bath. Remove the stopper and place the flask on a steam bath for 15 minutes.

• Continue to swirl the flask at frequent intervals.Make a spot test by withdrawing some of the reaction mixture on the tip of a stirring rod and touching it to a filter paper; permanganate, if present will appear as a purple ring around the dark brown spot of manganese dioxide

Filter the mixture through a large Buchner

• . If permanganate is still present, add 1 mL of methanol and heat. Repeat this procedure until the permanganate colour has disappeared..

Filter the mixture through a large Buchner

• Filter the mixture through a large Buchner funnel (vacuum) into a clean filter flask. Rinse the reaction flask with 10 mL of hot 1% sodium hydroxide solution and pour through the filter. Repeat with a second portion of 10 mL of 1% sodium hydroxide solution.

Filter the mixture through a large Buchner

acidify to about pH 1 by cautiously

• Place the filtrate and washings in a 250 mL beaker (premarked at 10 mL), add a boiling chip and boil over a flame until the volume of the solution is about 10 mL.

Cool the solution in an ice-water bath and acidify to about pH 1 by cautiously adding concentrated hydrochloric acid dropwise while stirring the solution. (SAFETY GLASSES!) Add an additional 3 mL of acid, stir and allow the beaker to stand in the ice bath for 5 - 10 min to complete the crystallisation.

Recrystallize

• Collect the acid by vacuum filtration. Recrystallize it from not more than 5 mL of boiling water (if 2 mL of cyclohexene was used). Cool to room temperature, then place in an ice-water bath for 10 minutes.

Recrystallize

Recrystallize

• Filter the product by vacuum (Hirsch funnel) and dry as described under Technical Points. Measure the melting point and yield of product. Calculate the percentage yield. Submit your sample in a labelled vial along with your report.

Infrared Spectroscopy

On your worksheet indicate the important differences in the i.r. spectrum of the starting material and product. Relate the values of these absorptions to the structures of the compounds (see Appendix 3).

Animations of the vibrational modes have been calculated for both cyclohexene and adipic acid.

VIBRATIONAL MODES

• http://wwwchem.uwimona.edu.jm/spectra/JSpecView/iranim/index.html