103-72-0

colourless to pale yellow liquid with a penetrating odour

As Derivatizing reagent for primary and secondary amines, Phenyl isothiocyanate can be used in sequencing peptides by Edman degradation and in amino acid analyses by HPLC.

Derivatizing agent for primary, secondary amines. In sequencing of peptides by Edman degradation. In amino acid analyses by HPLC (Pico-Tag).

ChEBI: An isothiocyanate having a phenyl group attached to the nitrogen.

Synthetic procedure for phenyl isothiocyanate in 1-mol scale
Into a 2-L jacketed flask, 91.2 g of CS2 (1.2 mol) was dropwise added to a mixture of aniline (93.0 g, 1.0 mol) and K2CO3 (276.0 g, 2.0 mol) in 700 mL of water at room temperature within a period of 2.5 h. After the addition was complete, the mixture was stirred another 2 h. Then, the mixture was cooled to 0 °C, and a solution of 92.3 g of TCT (0.5 mol) in 450 mL of CH2Cl2 was dropwise added within 4 h. After the addition was complete, the mixture was stirred another 1 h to complete the conversion. The resulting mixture was basified to pH >11 with 250 mL of 6 N NaOH and yielded a clear solution. The organic layer was separated and the aqueous layer was extracted with 150 mL of CH2Cl2. The combined organic layers were dried over anhydrous Na2SO4, filtered, and the solvent of filtrate was removed via distillation under atmospheric pressure with a 25-cm Vigreux column. The residue was vacuum distilled and the desired product fraction was collected at 72–74 °C/1 mmHg. Finally, 127.0 g of colorless liquid (94%) was obtained.

Phenyl isothiocyanate (PITC) is a well-established reagent in protein chemistry since its introduction in Edman degradation. PITC reacts with primary and secondary amines under alkaline conditions within 20 min. The resulting phenylthiocarbamyl (PTC) derivatives of the amino acids are stable and do not interfere with reaction by-products during chromatography. The absorption maximum is around 245 nm with a detection limit of 1 pmol.
Phenyl isothiocyanate may be employed as a derivatization reagent for high-performance liquid chromatographic (HPLC) analysis of various amphetamine derivatives in body fluids for forensic purposes.

Tetrahedron Letters, 38, p. 1597, 1997 DOI: 10.1016/S0040-4039(97)00121-4
Synthesis, p. 300, 1989 DOI: 10.1055/s-1989-27231
Tetrahedron Letters, 23, p. 447, 1982 DOI: 10.1016/S0040-4039(00)86856-2

It is insoluble in H2O, but soluble in Et2O and EtOH. If impure (due to formation of thiourea), then steam distil it into a receiver containing 5-10mL of N H2SO4. Separate the oil, dry over CaCl2 and distil it under vacuum. [Dains et al. Org Synth Coll Vol I 447 1941, Beilstein 12 IV 867.]