A Triphenylmethanol

Drain the lower aqueous layer into a beaker. Pour the remaining ether layer that contains the triphenylmethanol product into a dry Erlenmeyer flask. Pour the aqueous layer back into the separatory funnel and reextract it with 5 mL of ether. Remove the lower aqueous phase and discard it. Combine the remaining ether phase with the first ether extract. Dry the ether solution with granular anhydrous sodium sulfate (Technique 12, Section 12.9). 

Crystallize your entire product from hot isopropyl alcohol in an Erlenmeyer flask using a hot plate as the heating source. Be sure to add the hot alcohol in small portions to the crude product. Add the hot solvent until the solid just dissolves. Then allow the flask to cool slowly. When it has cooled, place the flask in an ice bath to complete the crystallization. Collect the solid on a Hirsch funnel and wash it with a small amount of cold isopropyl alcohol. Set the crystals aside to air-dry. Report the melting point of the purified triphenylmethanol (literature value, 162°C) and recovered yield in grams. Submit the sample to the instructor in a properly labeled vial. 

At the option of the instructor, determine the infrared spectrum of the purified material in a KBr pellet (Technique 25, Section 25.5). Your instructor may assign certain tests on the product you prepared. These tests are described in the Instructor s Manual. 

When the phenylmagnesium bromide has cooled to room temperature, use a Pasteur pipette to transfer this reagent as quickly as possible to 4 g of crushed dry ice contained in a beaker. The dry ice should be weighed as quickly as possible to 

Exercise caution in handling dry ice. Contact with the skin can cause severe frostbite. Always use gloves or tongs. The dry ice is best crushed by wrapping large pieces in a clean, dry towel and striking them with a hammer or a wooden block. It should be used as soon as possible after crushing it to avoid contact with atmospheric water. 

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Table 20-1. N-Substituted imidazoles and triazoles prepared by transfer reactions of azolides A—F with tertiary alcohols of the triphenylmethanol type and analogues.

Labelling the aliphatic carbon atom with (53%) allowed comparison of the nuclear magnetic C -shifts of the covalent sp -hybridized triphenyl-C -methanol (in tetrahydrofuran solution) with that of the labelled triphenylcarbonium ions, (C8Hg)3C HS07 (triphenyl-C -methanol in sulphuric acid solution). A shift of 129-6 p.p.m. to lower shielding was observed in the triphenylcarbonium ion, as compared with the covalent triphenylmethanol. 

Example The extraordinary stable trityl ion, PhsC, m/z 243, tends to dominate mass spectra (Chap. 6.6.2). Thus, neither the El spectrum of chlorotriphenyl-methane nor that of its impurity triphenylmethanol show molecular ions (Fig. 8.11). An isobutane PICI spectrum also shows the trityl ion almost exclusively, although some hint is obtained from the Ph2COH ion, m/z 183, that cannot be explained as a fragment of a chlorotriphenylmethane ion. Only FD reveals the presence of the alcohol by its molecular ion at m/z 260 while that of the chloride is detected at m/z 278. Both molecular ions undergo some OH or Cl loss, respectively, to yield the Ph3C fragment ion of minor intensity. 

Carbocations are a class of reactive intermediates that have been studied for 100 years, since the colored solution formed when triphenylmethanol was dissolved in sulfuric acid was characterized as containing the triphenylmethyl cation. In the early literature, cations such as Ph3C and the tert-butyl cation were referred to as carbonium ions. Following suggestions of Olah, such cations where the positive carbon has a coordination number of 3 are now termed carbenium ions with carbonium ions reserved for cases such as nonclassical ions where the coordination number is 5 or greater. Carbocation is the generic name for an ion with a positive charge on carbon. 

Triphenylmethyl fluoroborate is prepared by dissolving 27 g. (0.104 mole) of triphenylmethanol ( purum, Fluka A G) in 260 ml. of propionic anhydride by warming on a steam bath. With an acetone-dry ice bath the solution is cooled to 10° and maintained between 10° and 20° while 31 ml. of 43% w/w fluoroboric acid is added portionwise with swirling. The yellow solid is collected, washed well with dry ether, and dried in a desiccator under vacuum to yield 34 g. (90-99%). The product is very hygroscopic, taking up water with hydrolysis. It is desirable to prepare this reagent immediately before use. 

Triphenylmethanol (45.0 g, 0.17 mol) is added with swirling, giving a bright yellow-orange suspension. The amount of precipitate is increased by adding ethyl acetate (600 mL). Care must be takent to avoid use of an ether in place of ethyl acetate in this step, as this substitution promotes spectacular decomposition of the product. 

In a subsequent study, Shudo and co-workers244 showed that benzaldehydes with electron-withdrawing groups (N02, CF3) react with 2 equivalents of benzene in the presence of triflic acid to give substituted triphenylmethanes in good yields [Eq. (5.90)]. They also observed that pura-fluorobenzaldehyde and biphenyl-4-carboxaldehyde yield diphenylmethane and triphenylmethanol under similar conditions, and the same products were also isolated in the reaction of triphenylmethane (Scheme 5.29). 

Triphenylmethyl bromide, m.p. 153-154 °C, may be prepared in a similar manner from triphenylmethanol and acetyl bromide. 

ROH — RSH. This transformation can be effected with this reagent (1) in moderate to high yield. The yield is quantitative in the case of triphenylmethanol C.H5)3COH], but some dehydration is observed with tertiary alcohols possessing a-methyl or a-benzyl group. 

Oxidative decarboxylation.1 Sodium hypochlorite is known to effect oxidative decarboxylation of a-hydroxy carboxylic acids to form ketones and C02, but a hydroxyl group is not essential since trisubstituted acetic acids are also subject to this oxidation. Thus triphenylacetic acid is oxidized by NaOCl to triphenylmethanol and benzophenone. In the presence of a phase-transfer catalyst, the rate is enhanced... 

When triphenylmethanol is dissolved in concentrated sulfuric acid, a solution with an intense yellow color is formed. The yellow species is the triphenylmethyl carbocation, formed by the following reaction ... 

Triphenylmethanol is insoluble in water, but when it is treated with concentrated sulfuric acid, a bright yellow solution results. As this yellow solution is diluted with water, its color disappears and a precipitate of triphenylmethanol reappears. Suggest a structure for the bright yellow species, and explain this unusual behavior. 

Dynamic properties of the hydrogen bonding arrangement in a selectively deuterated sample of solid triphenylmethanol (Ph3COD) have been studied using solid state 2H NMR [177,178]. In the crystal structure (Fig. 10), the molecules form hydrogen bonded tetramers, with the oxygen atoms positioned approximately at the corners of a tetrahedron [179]. 

During concentration, a precipitate of diphenylprolinol sulfate and triphenylmethanol is formed. Caution Benzene (43 g), formed during the quench of the excess phenylmagnesium chloride, is removed during the concentration. 

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