Phenyl isothiocyanate

Structural formula
General
Surname	Phenyl isothiocyanate
other names	Isothiocyanatobenzene ( IUPAC ) Phenyl mustard oil Thiocarbanil Edman's reagent
Molecular formula	C 7 H 5 NS
Brief description	colorless to yellowish, tear-irritating liquid with a pungent, mustard-like odor
External identifiers / databases
CAS number 103-72-0 EC number 203-138-1 ECHA InfoCard 100,002,853 PubChem 7673 Wikidata Q422311
properties
Molar mass	135.19 g mol −1
density	1.13 g cm −3 (20 ° C)
Melting point	−21 ° C
boiling point	218-221 ° C
Vapor pressure	10 hPa (20 ° C)
solubility	Decomposes in water
Refractive index	1.6492 (23 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 301-314-317-334-410 P: 260-280-301 + 310-303 + 361 + 353-304 + 340-305 + 351 + 338-333 + 313-342 + 311-363
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Phenyl isothiocyanate (PITC) is a chemical compound that is used as a reagent for chemical analysis ( Edman reagent ) and synthetic organic chemistry. The other name phenyl mustard oil is due to the relationship with the flavor carrier of mustard, allyl isothiocyanate (CH ₂ = CH − CH ₂ N = C = S).

presentation

Aniline reacts with carbon disulfide in ethanol and finely divided potassium hydroxide as a catalyst to form diphenylthiourea. This reaction presumably proceeds via the intermediates phenyldithiocarbamic acid and phenylisothiocyanate with elimination of hydrogen sulfide . From the diphenylthiourea formed, phenyl isothiocyanate is formed in the next step on exposure to acids with elimination of aniline:

Another method for the preparation of phenyl isothiocyanate also starts from aniline and carbon disulfide in concentrated ammonia solution. The salt ammonium phenyldithiocarbamate, isolated as an intermediate, is converted into phenyl isothiocyanate with lead nitrate :

properties

Phenyl isothiocyanate is a colorless to yellowish liquid with a pungent, mustard-like odor that causes tears in the eyes. The compound boils at 221 ° C. under normal pressure. According to Antoine, the vapor pressure function results accordingly

${\displaystyle \log _{10}\left(P(T)/{\text{bar}}\right)\;=\;A-{\frac {B}{T+C}}\qquad {\text{mit}}\qquad {\begin{cases}A=4{,}44210\\B=1930{,}513~{\textrm {K}}\\C=-58{,}467~{\textrm {K}}\end{cases}}}$

in the temperature range from 320 K to 491 K.

The compound reacts violently with alcohols , amines , acids , bases , water and oxidizing agents .

use

It is used as a mobile phase in reversed-phase high-performance liquid chromatography for the analysis of secondary amines and is used in synthetic chemistry as a reagent in Edman degradation and is therefore called the "Edman reagent".

Individual evidence

1. ↑ ^{a b} Entry on phenyl isocyanate. In: Römpp Online . Georg Thieme Verlag, accessed on June 13, 2014.
2. ↑ ^{a b c d e f g h i} Entry on phenyl isothiocyanate in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
3. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-428.
4. ↑ L. F. Fieser, M. Fieser: Textbook of organic chemistry . 3. Edition. Verlag Chemie, 1957, p. 703 .
5. ↑ FB Dains, RQ Brewster, CP Olander: phenyl isothiocyanate In: Organic Syntheses . 6, 1926, p. 72, doi : 10.15227 / orgsyn.006.0072 ; Coll. Vol. 1, 1941, p. 447 ( PDF ).
6. ↑ D. R. Stull: Vapor Pressure of Pure Substances Organic Compounds . In: Ind. Eng. Chem . tape 39 , 1947, pp. 517-540 . , doi : 10.1021 / ie50448a022