1-aminoalkylphosphonic acids used as standards were from our collection. Most of them are also available from the Acros Catalogue [www.acros.com] (see for example: 29164, 29165, 34477, 34478, 34481, 34479, 34491).
Preparation of triphenylmethylamine13
Finely powdered solid chlorotriphenylmethane (trityl chloride) (28 g, 0.10 mole) was introduced in small portions to a vigorously stirred solution of ammonium chloride (10.8 g, 0.20 mol) in 25% of aqueous ammonia (100 cm3) at the temperature about 0 oC (ice-water bath). Then, the reaction mixture was stirred 12-24 hrs, white precipitate was removed by suction, washed with water (5 x 20 cm3), and dried “on air” to give a crude Ph3CNH2 which contains about 10-15% of Ph3COH. If a practically pure Ph3CNH2 is needed, the following procedure is recommended: A solution of chlorotriphenylmethane (278.5 g, 1.00 mol) in toluene (1000 cm3) was introduced dropwise to a vigorously stirred solution of ammonium chloride (saturated, but at least 53.5 g, 1.0 mol) in 25% of aqueous ammonia (1000 cm3) at temperature about 0 oC (ice-water bath). Then, the reaction mixture was stirred vigorously for about 24 hrs at the temperature about 20 oC, organic phase was separated, dried over Na2SO4, then after removing of inorganic salt by suction, a solvent was evaporated under “vacuo” from water bath at the temperature below 70 oC. The warm oily residue was stirred in the same flask on rotavap, and hexane (about 800 cm3) was introduced portion-wise to cause a crystallization of Ph3CNH2. The crystallizing mixture was stirred additionally for about 30 minutes, then the crystalline precipitate was removed by suction, washed with a cold hexane (3 x 100 cm3), dried “on air” to give 233-246 g (90-95% of yield) of triphenylmethylamine with purity between 95-98% (assayed by 1H NMR or by titration with HClO4 in water/acetone). Pure triphenylmethylamine could be obtained by precipitation of its hydrochloride.
Synthesis of 1 aminoalkylphosphonic acids. General procedure A
Phosphorus trichloride (8.8 cm3, 0.10 mol) was added drop-wise to acetic acid (50 cm3) at temperature below 20 oC (a cold water bath was used), then the solution was stirred additionally for about 30 minutes, cooled to about 0 oC (ice-water bath) and finely powdered N- (triphenylmethyl)alkanimine (0.10 mol) was added portion-wise with vigorous stirring (PTFE stirring shaft with blade was used). The reaction mixture was stirred additionally for about 30 minutes at the same temperature, then it was gradually heated to about 100 oC (water bath) under reflux condenser connected to the HCl absorber. After about 1 hr of heating, the volatile material was removed by evaporation, and oily residue was treated with water (100 cm3) and stirred for about 15 minutes. The precipitated triphenylmethanol was separated by suction and washed with water (4 x 10 cm3). Collected filtrates were evaporated to give crude oily 1- acetylaminoalkylphosphonic acids 1a-j (identified by means of 1H and 31P NMR). Oily residue was treated with 6M of hydrochloric acid (200 cm3), and refluxed gently for about 8 hrs. The hydrolysate was evaporated, residue was dissolved in methanol (50 cm3) and the 1- aminoalkylphosphonic acid was precipitated by drop-wise addition of methyloxirane (propylene
