Alcohols are ubiquitous in biologically active organic compounds as well as industrially useful mate — Organic Chemistry Chemistry Question

Alcohols are ubiquitous in biologically active organic compounds as well as industrially useful materials. A key method of preparing alcohols in synthetic organic chemistry is to reduce carbonyl compounds such as aldehydes and ketones. A variety of reagents have been developed for such conversions, and one of the most common reagents used in laboratories is sodium borohydride. This reagent is a mild and selective reducing agent for ketones and aldehydes. Reduction of cyclohexanone (A) with sodium borohydride gives cyclohexanol (B), for example, with a good yield and as a single product (eq. 1). Sodium borohydride can also reduce 4-tert-butylcyclohexanone (C) to 4-tert-butylcyclohexanol, a mixture of two isomers D and E (eq. 2). This can be understood based on the existence of two approach pathways for the hydride in sodium borohydride, i.e., the axial and equatorial directions.

In this experiment, you will reduce the 4-tert-butylcyclohexanone (C) with sodium borohydride and analyze the products on thin layer chromatography (TLC).

[VISUAL]

Chemicals
* anhydrous sodium sulphate
* anisaldehyde stain (10% p-anisaldehyde and 5% H₂SO₄ in methanol)
* ethyl acetate, liquid
* ethanol
* hexane, liquid
* sodium borohydride, solid
* sulfuric acid solution
* 4-tert-butylcyclohexanone, solid

Apparatuses and glassware
* crystallization dish
* Erlenmeyer flask (30 cm₃)
* filter paper
* glass capillary
* glass funnel
* magnetic stirrer
* magnetic stirring bar (1.5 cm long)
* oven (or hot-plate)
* test tube (diameter: ca. 2 cm, height: ca. 20 cm or taller)
* TLC plate (silica gel 60; layer thickness: 0.25 mm, on a glass support)
* Tweezers
* water bath
* wide-mouth bottle with cap (developing chamber)
* wide-mouth bottle (anisaldehyde stain container)
* graduated pipette

Procedures
(1) Inside a fume hood, add 4-tert-butylcyclohexanone (1.0 g) and ethanol (1 cm₃) to a test tube fitted with a stirring bar. Place the test tube in a water bath on a magnetic stirrer. Stir the mixture to form a clear solution at room temperature (ca. 25 °C). Add sodium borohydride (0.1 g) to the resulting solution, in a few portions. Take care to regulate the temperature.
(2) Monitor the progress of this reaction with TLC according to the procedure described in Problem 39 above. Develop TLC plates with an developer of hexane/ethyl acetate = 4/1. Dip the TLC plates fully in the anisaldehyde stain solution stored in a wide-mouth bottle for a few seconds. Take the plates out of the solution and heat them in an oven at 150 °C or above for 15 min (or heat them on a hot-plate until the spots become visible). Use tweezers for these processes. Check the completion of the reaction by TLC.
(3) Remove the water bath. Add water (3 cm₃) and hexane (3 cm₃) to the reaction mixture. Vigorously stir the entire mixture for 5 min. Then transfer the upper layer (organic phase) to an Erlenmeyer flask using a graduated pipette.
(4) Add hexane (3 cm₃) to the test tube with the remaining lower layer (aqueous phase) and stir the mixture vigorously for 5 min. Transfer the upper layer (organic phase) to the same Erlenmeyer flask using the graduated pipette. Repeat this extraction process again.
(5) Add anhydrous sodium sulfate (1 g) to the Erlenmeyer flask containing the organic phase. Filter this mixture using filter paper and a glass funnel to remove the solids. Transfer the filtrate to a crystallization dish. Rinse the residual solids with hexane (2 cm₃). Transfer the washing to the crystallization dish.
(6) Evaporate the ethanol and hexane in the fume hood at room temperature (it will take several hours) to obtain a white solid. Weigh the amount of solids.