FORM 2
The Patent Act 1970,
(39 of 1970)
&
The Patent rule 2003
Complete Specification
(See Section 10 and Rule 13)
1. TITLE OF THE INVENTION
" A PROCESS FOR THE PREPARATION OF ISOPROPYL PHENOL FROM NITRO CUMENE "
2. APPLICANT(S)
(a) NAME : GHARDA CHEMICALS LIMITED
(b) NATIONALITY : INDIAN
(c) ADDRESS: B-27/29, MIDC PHASE-1, DOMBIVLI, DIST. THANE, PIN 421 203, INDIA
3. PREAMBLE OF THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

TITLE
A PROCESS FOR THE PREPARATION OF ISOPROPYL PHENOL FROM NITRO CUMENE
BACKGROUND AND SUMMARY OF THE INVENTION:
There has been a demand for selective alkylation of phenols in the 2-position to the hydroxyl group. With respect to the manufacture of 2-isopropyl phenol, there have been, to date, patents and papers published. Most of the reports indicate preparation of 2-alkyl phenol by reacting phenol with an olefin in presence of alumina based catalyst at high temperatures ( 200-380°C) and either normal or elevated pressure.(Ref: GB 1212579). 2 and 4 position substitution generally occurs in presence of catalysts such as zinc chloride, boron trifluoride, sulfuric acid or fuller's earth.(Ref: FR 1599373A, DE 1815846C3). 2-isopropyl phenol is a useful intermediate in the field of agrochemicals, UV stabilizers, polymerization inhibitors and anti-oxidants. Its methyl derivative (2-isopropyl anisole) is used in the fragrance chemical industry (Ref: JOC, 1990, Vol 55, 3541). According to the present invention, there is provided a novel process for the synthesis of 2-isopropyl phenol starting from 2- nitro cumene. 2-Nitro cumene is a by product obtained during nitration of cumene. Cumene treated with nitric acid, by addition of the mixed acid at 0-25DC gives a maximum yield of 94.5% mono nitro cumenes. The isomers are separated by fractionation wherein, the top composition, the low boilers, comprising of 75% 2-nitro cumene, 20% 3-nitro cumene and 5% 4-nitro cumene is obtained as a by-product and the bottom still is rich in 4- nitro cumene. Methods of purification are reported in literature involving successive fractionation method (Ref: J. of lnd.& Engg. Chem; (1951) , 43, 2355-62) for the purification of waste isomers of nitro cumenes, which also yields high purity 3-isomer and 4-isomer thus making the process operable with maximum economic viability, which is a considerable advantage from a cost stand point, especially for industrial scale plants.
A process, for the preparation of isopropyl phenol starting from 2- nitro cumene, which consists of hydrogenation of high purity 2-nitro cumene to yield 2-cumidine, which is further subjected to diazotization and hydrolysis to yield 2-isopropyl phenol.
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DETAILED DESCRIPTION OF THE INVENTION
In the present invention resides a process which consists of hydrogenation of high purity 2-nitro cumene to yield 2-cumidine, which is further subjected to diazotization and hydrolysis to yield 2-isopropyl phenol. 2-nitro cumene is hydrogenated in presence of surface active catalysts such as 5% palladium on carbon, or 1% Platinum on carbon or Raney Ni at temperatures ranging from 80-150°C, preferably at 100-130X and hydrogen pressure ranging from 5-20kg/cm2 .The reaction may be carried out in presence of solvents, preferably aromatic hydrocarbons, but more preferably, it may be carried out in the absence of solvents, to yield 2-cumidine in high yield and purity. The said catalyst can be recycled in the subsequent batches. The 2-cumidine is then isolated and subjected to diazotization. Diazotization is carried out by a procedure known to those skilled in the art, at temps, ranging from -5 to 30°C preferably, -5 to 5°C. However, for better reaction rates, it may be carried out at 0-5°C. The diazonium salt is then carefully hydrolyzed at temps, ranging from 50-150°C, preferably at 105-110°C to yield 2-isopropyl phenol The inventors have thought of this process as an outlet for the by products formed during industrial nitration of cumene. The present process does not deploy high operating temperatures and pressures as in the conventional methods for the manufacture of alkyl phenols.
The following examples illustrate the way in which the process of the invention may be
carried out in practice.
Example 1 : Preparation of 2-cumidine:
2- nitro cumene (fractionated, purity >99%) is charged into an SS autoclave along with
Raney Ni catalyst ( 5 gm/m) and heated to 130°C. Hydrogen is bubbled into the mass and
the system is pressurized with 15 kg/cm2 H2.lt is maintained at 130°C till hydrogen
consumption tends to cease. The reaction mass is discharged and separated from the
catalyst. The product is isolated by distillation in a yield of 90%. Purity >99% by HPLC.
Example 2 : Preparation of 3-cumidine:
3- nitro cumene (fractionated, purity >99%) is charged into an SS autoclave along with
Raney Ni catalyst (10 gm/m) and heated to 125°C. Hydrogen is bubbled into the mass and
the system is pressurized with 20 kg/cm2 H2.lt is maintained at 130°C till hydrogen
consumption tends to cease. The reaction mass is discharged and separated from the
2-

catalyst. The product 3-cumidine is isolated by distillation in a yield of 90%. Purity >99% by HPLC.
Example 3 : Preparation of 4-cumidine:
4- nitro cumene ( purity >99%) is charged into an SS autoclave along with Raney Ni catalyst ( 10 gm/m) and heated to 125°C. Hydrogen is bubbled into the mass and the system is pressurized with 20 kg/cm2 H2.lt is maintained at 130°C till hydrogen consumption tends to cease. The reaction mass is discharged and separated from the catalyst. The product 3-cumidine is isolated by distillation in a yield of 92%. Purity >99% by HPLC.
Example 4 : Preparation of 2-isopropyl phenol:
135 gm of 2-cumidine is added to a mixture of 200 gm 98% sulfuric acid and 1 lit. water at 35 to 40°C. The reaction mass is stirred at 35°C for 1 hr. and then cooled to 0°C.A solution of 74 gm NaN02 in 200 ml water is added to the reaction mass, maintaining temp.0-5°C. The excess nitrite is destroyed and the reaction mass is slowly added to a mixture of 290 gm CuS04 and 250 ml water at 105°C. The product formed is simultaneously steam distilled. Yield of 2-isopropyl phenol obtained = 60% .Purity of the product = 95%.
Example 5 : Preparation of 3-isopropyl phenol:
135 gm of 3-cumidine is added to a mixture of 250 gm 98% sulfuric acid and 1 lit. water at 35 to 40°C. The reaction mass is stirred at 35°C for 1 hr. and then cooled to 0°C.A solution of 74 gm NaN02 in 200 ml water is added to the reaction mass, maintaining temp.5°C. The excess nitrite is destroyed and the reaction mass is slowly added to a mixture of 290 gm CuS04 and 250 ml water at 105°C. The product formed is simultaneously steam distilled. Yield of 3-isopropyl phenol obtained = 55% .Purity of the product = 95%.
Example 6 : Preparation of 4-isopropyl phenol:
135 gm of 4-cumidine is added to a mixture of 200 gm 98% sulfuric acid and 1 lit. water at 50°C. The reaction mass is stirred at 50°C for 1 hr. and then cooled to 0°C.A solution of 74 gm NaN02 in 200 ml water is added to the reaction mass, maintaining temp.5°C. The excess nitrite is destroyed and the reaction mass is slowly added to a mixture of 290 gm CuS04 and 250 ml water at 105°C. The product formed is simultaneously steam distilled. Yield of 3-isopropyl phenol obtained = 55% .Purity of the product = 95%.
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CLAIMS We Claim
1. A process for preparing isopropyl phenols starting from nitro cumenes which comprises of reducing the nitrocumenes using hydrogen in presence of surface active catalysts such as palladium on carbon, or Platinum on carbon or Raney Ni followed by diazotization and hydrolysis.
2. A process as claimed in claim 1, in which the said catalyst is Raney nickel.
3. A process as claimed in claim 1 and 2, in which the hydrogenation is carried out at
120 to 140° C.
4. A process as claimed in claim 1 and 2, in which the hydrogenation is carried out
under 10 to 20 kg/cm2 hydrogen pressure.
5. A process as claimed in claim 1, where the diazotization is carried out at 0-5°C.
6. A process as claimed in claim 1, in which hydrolysis of the diazonium salt of
cumidine is carried out at 105 to 110°C to yield the isopropyl phenols.

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ABSTRACT:
2-isopropyl phenol, a useful building block for the manufacture of agrochemicals, UV stabilizers, polymerization inhibitors and anti-oxidants, is prepared, starting from o-nitro cumene (ONC) in high yield and purity by hydrogenation, followed by diazotization and hydrolysis.2-nitro cumene is a by product obtained in the nitration of cumene which is industrially practiced by the inventor for manufacture of herbicide isoproturon. This byproduct comprising of isomers of nitro cumene is purified and converted to 2-isopropyl phenol by a novel process by the following scheme: