Oxidation of 9-Fluorenol

Abstract

The objective of this lab was to synthesize a molecule that is used in the food and flavours industry. This was achieved through an esterification reaction between an unknown alcohol, Alcohol D, and carboxylic acids (acetic acid) to produce an ester. The slow and reversible reaction was catalyzed by a very strong acid; sulphuric acid. After the crude product was obtained, the ester was purified with the use of several compounds. The final product was analyzed in infrared spectrometry (IR), proton nuclear magnetic resonance (1H-NMR), and mass spectroscopy (MS). The structure was determined to be 3-methylbutyl-ethanoate.

Introduction

The purpose of this lab experiment was to first synthesize an unknown ester using an unknown alcohol and a known carboxylic acid. The ester was then identified through the application of three analytic techniques: infrared spectrometry (IR), proton nuclear magnetic resonance (1-H NMR), and mass spectroscopy MS. These spectrums assisted in the identification of the final ester and the unknown structure of the alcohol. The synthesized ester was a molecule with very high organoleptic properties. Organoleptic substances are common to the industry; they are useful in fabricating consumer products. Generally, organoleptic materials are substances with sensory properties, such as an odour, taste, colour, or feel. One of the most important industries that rely on organoleptic substances to flavour, or impart/improve odours to materials-- is the food industry. They rely heavily on a wide range of organoleptic substances to make products more appealing to customers. This reliance comes at a cost. Complex mixtures obtained as oil extract from natural products are expensive. Therefore, it is optimal to use single molecules with strong organoleptic properties.

The production of an organoleptic molecule involves an equilibrium reaction between a carboxylic acid and an alcohol. The procedure is based on an equilibrium reaction. In order for the equilibrium reaction to proceed to completion, excess carboxylic acid is added. Carboxylic acid was specifically chosen to be the reagent in excess because; it is less expensive and much more easily removed from the reaction mixture. By taking advantage of the products low water solubility, the excess acid and alcohol that didn't react are removed by extraction with water during the isolation procedure. Any remaining traces of the acid is removed by extraction using aqueous sodium bicarbonate and then dried over anhydrous sodium sulphate.

Sulphuric acid (H2SO4), is a strong mineral acid which is highly corrosive, and soluble in water. It was required in the experiment in order to speed up the reaction to completion. This is because the sulphuric acid acted as a catalyst in the reaction. The sodium sulphite was required to dry the product, whereas, sodium bicarbonate was used to wash the crude product. And lastly, sodium chloride was required in the final extraction step.

The various chemical compounds used in this experiment underwent two processes: distillation and Fischer esterification. Distillation is a method of separating mixtures based on differences in their volatilities in a boiling liquid mixture. On the other hand, Fischer esterification (Figure 1) is a special type of esterification that involves refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst.

Materials

The materials used in the experiment included: a 100ml round bottom boiling flask, two ceramic boiling stones, a short path distillation head with thermometer and condenser as well as a reflux condenser. A 250ml separatory funnel was used to separate the two phases of the solution. A Buchner funnel and filtering flask and Whatman #4 Filter paper were used to vacuum filter the precipitate; the final product was then put into a glass sample vial. The chemicals used in the experiment were: 20ml of glacial acetic acid; 15ml of an unknown alcohol, labelled as Alcohol D, as well as 4ml of concentrated Sulphuric acid; 50ml of sodium bicarbonate and 25ml of saturated sodium chloride solution and 65ml of cold water. Sodium sulphate and silica were used during the filtering process.

Method

Lab One:

The initial step was to place 15ml of Alcohol D and 20ml of acetic acid into the 100ml round bottom boiling flask. After the alcohol and the carboxylic acid were mixed, 4ml of concentrated sulphuric acid was carefully added into the solution. Two ceramic boiling stones were then added and a reflux condenser was attached to the round bottom flask. The solution was then refluxed with a heating mantle that was attached to a resistor which reduced the current to approximately forty percent. Once the mixture was refluxed for an hour, the solution had turned to a dark purple colour and it was left to cool to room temperature. The mixture was then transferred to a separatory funnel and 55ml of cold water was also added to the mixture. The 100ml round bottom flask was then rinsed with 10ml of cold water to obtain the rest of the residual, which was then added to the separatory funnel. The mixture was carefully mixed with inversion twenty to thirty times to avoid the formation of an unbreakable emulsion. Two phases were formed: the top phase was a dark purple non-aqueous phase and the bottom phase was a light purple aqueous phase. After the two phases clearly separated, the lower aqueous phase was drained. 25ml of five percent sodium bicarbonate solution was then carefully added to the separatory flask since carbon dioxide was produced. The mixture was then mixed by inversion twenty to thirty times with the escape valve being opened every three inversions to allow carbon dioxide to leave the system; then the lower aqueous phase was drained off. The drained aqueous phase was tested with litmus paper to determine the pH of the mixture; which turned out to be acidic. The procedure of adding 25ml of bicarbonate was repeated along with inversion and the aqueous solution drained off. Once the aqueous solution was tested to be basic; 25ml of saturated sodium chloride solution was added to the mixture to remove any left-over water in the product and once again, the lower aqueous phase was removed. The product was then filtered through filter paper on the glass funnel twice: once with 1.2g of sodium sulphate and then with 1.2g of silica. The product was