3
This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung 4.0 Lizenz. 468 R. Gopal et al. • Synthesis of Phthaleins Synthesis of Phthaleins with a Chiral Carbon Atom R. Gopal, P. C. Gupta, V. P. Aggarwala, and S. P. Garg Department of Chemistry, University of Allahabad, Allahabad (India) (Z. Naturforsch. 28 b. 468-470 [1973]; received September 20, 1972/January 23, 1973) Phenyl, phenol, phthaleine, resorcinol, pyrogallol, orcinol Phthaleins (PE) with a chiral carbon atom — phenyl phenol PE, phenyl resorcinol PE, phenyl catechol PE, phenyl quinol PE, phenyl pyrogallol PE, phenyl phloroglucinol PE and phenyl orcinol PE have been obtained by condensing 2-benzoyl benzoic acid with appropriate phenols. The structure of phenyl resorcinol phthalein, which was found to exist in two isomeric forms, based on chemical reactions and spectral data has been discussed. The AmBx values for most of the dyes were found higher than their analogous phthaleins. 2-Benzoyl benzoic acid (1) has been found to exist in two isomeric forms 1 and 2. The existence of cyclic form (lactol) has been confirmed by various workers1-7. The lactol condenses with phenols gi ving a new series of phthaleins (3). The condensation process proceeds through the equilibrium process of lactol ( 2 ) of acid (1) and with excess of phenol whole of the acid reacts as lactol. 1 2 3 4 Ri = R 2 = R 4 = Rs = H, R 3 = OH; 5 R 2 = R 4 = Rs = H, Ri = R 3 = OH; 6 R3 = R4 = Rs = H, R1=R2=OH; 7 R 2 = Ra = Rs = H, Ri = R 4 = OH; 8 R 2 = R 4 = H, Ri = R 3 = R 5 = OH; 9 R4 = Rs = H, Ri = R 2 = R 3 = OH; 10 Ra = R 4 = H, Rs = CH3, Ri = R 3 = OH; 11 R 2 = R 4 = R 5 = H, Ri = R 3 = OCOCH3; 12 R 5 = H, R 2 = R 4 = Br, Ri = R 3 = OH. The column chromatography, supplemented with TLC was used for the purification of condensed pro ducts. Their IR spectra show strong bands between 1770 —1760 cm-1 due to v-lactone. The compound (4) has also been prepared by the method of Hubacher8 and the two products were found to be identical (mixed m. p., superimposable IR spectra and Rvalues). Phenyl resorcinol phtha lein (5), when treated with excess bromine in acetic acid, yielded acid (1) and sym-tribromoresorcinol. Requests for reprints should be sent to Dr. R. G opal , Defense Laboratory, Jodhpur (India). The cleavage of 5 was also observed by KOH fusion into acid (1) and resorcinol. The dye (5; band at 1770 cm-1) was reduced by Zn-dust and acetic acid into an acid, phenyl resorcinol phthalin* (13; 3300 — 2900 and 1710 cm-1 due to —COOH). The acid (13) when left overnight was found changed into original dye (5) confirmed by mixed m. p., superim posable IR and Amax-values. However, the acid (13) when acetylated in CO2 atmosphere gave diacetyl compound (14; 1710 cm-1). The diacetyl (11; 1760, 1200 and 1125 cm-1, v-lactone and phenolic acetate) and dibromo (12; 1760 cm-1) derivatives of (5) are also indicative of v-lactone and resorcinol molecule. The deep yellow compound (5; 1760 cm-1, lac- toid) when boiled with excess of 0.01 n . HC1 gave an isomeric bright red compound (15; 3600 —3020 and 1690 cm-1, -COOH and />-quinonoid) (c/. fluor escein)9. 11 12 15 * The nomenclature is according to The Chemistry of Carbon Compounds, Edited by E.H. R odd .V o I.III B, p. 1110, Elsevier, New York 1956.

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Page 1: @4, H 5zfn.mpdl.mpg.de/data/Reihe_B/28/ZNB-1973-28b-0468.pdfThis work has been digitalized and published in 2013 by V erlag Zeitschrift für Naturforschung in cooperation with the

This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution4.0 International License.

Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschungin Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung derWissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht:Creative Commons Namensnennung 4.0 Lizenz.

468 R. Gopal et al. • Synthesis of Phthaleins

Synthesis of Phthaleins with a Chiral Carbon Atom

R. G o p a l , P. C. G u p ta , V. P. A g g a r w a l a , and S. P. G a r g

Department of Chemistry, U niversity of Allahabad, Allahabad (India)

(Z. Naturforsch. 28 b. 468-470 [1973]; received September 20, 1972/January 23, 1973)

Phenyl, phenol, phthaleine, resorcinol, pyrogallol, orcinolPhthaleins (PE) w ith a chiral carbon atom — phenyl phenol PE, phenyl resorcinol PE,

phenyl catechol PE, phenyl quinol PE , phenyl pyrogallol P E , phenyl phloroglucinol PE and phenyl orcinol P E have been obtained by condensing 2-benzoyl benzoic acid with appropriate phenols. The structure of phenyl resorcinol phthalein, which was found to exist in two isomeric forms, based on chemical reactions and spectral d a ta has been discussed. The AmBx values for most of the dyes were found higher than their analogousphthaleins.

2-Benzoyl benzoic acid (1) has been found to exist in two isomeric forms 1 and 2. The existence of cyclic form (lactol) has been confirmed by various workers1-7. The lactol condenses with phenols gi­ving a new series of phthaleins (3). The condensation process proceeds through the equilibrium process of lactol (2) of acid (1) and with excess of phenol whole of the acid reacts as lactol.

1 2 3

4 R i = R 2 = R 4 = Rs = H, R 3 = OH;5 R 2 = R 4 = Rs = H, R i = R 3 = OH;6 R 3 = R 4 = Rs = H, R 1 = R 2 = O H ;7 R 2 = Ra = Rs = H, R i = R 4 = OH;8 R 2 = R 4 = H, R i = R 3 = R 5 = OH;9 R 4 = Rs = H, R i = R 2 = R 3 = OH;

10 R a = R 4 = H, Rs = CH3, R i = R 3 = OH;11 R 2 = R 4 = R 5 = H, Ri = R 3 = OCOCH3;12 R 5 = H, R 2 = R 4 = Br, R i = R 3 = OH.

The column chromatography, supplemented with TLC was used for the purification of condensed pro­ducts. Their IR spectra show strong bands between 1770 —1760 cm-1 due to v-lactone.

The compound (4) has also been prepared by the method of H u b a c h e r 8 and the two products were found to be identical (mixed m. p., superimposable IR spectra and Rvalues). Phenyl resorcinol phtha­lein (5), when treated with excess bromine in acetic acid, yielded acid (1) and sym-tribromoresorcinol.

Requests for reprints should be sent to Dr. R. G o p a l ,

Defense Laboratory, Jodhpur (India).

The cleavage of 5 was also observed by KOH fusion into acid (1) and resorcinol. The dye (5; band at 1770 cm-1) was reduced by Zn-dust and acetic acid into an acid, phenyl resorcinol phthalin* (13; 3300— 2900 and 1710 cm-1 due to —COOH). The acid (13) when left overnight was found changed into original dye (5) confirmed by mixed m. p., superim­posable IR and Amax-values. However, the acid (13) when acetylated in CO2 atmosphere gave diacetyl compound (14; 1710 cm-1). The diacetyl (11; 1760, 1200 and 1125 cm-1, v-lactone and phenolic acetate) and dibromo (12; 1760 cm-1) derivatives of (5) are also indicative of v-lactone and resorcinol molecule.

The deep yellow compound (5; 1760 cm-1, lac- toid) when boiled with excess of 0.01 n . HC1 gave an isomeric bright red compound (15; 3600 — 3020 and 1690 cm-1, -COOH and />-quinonoid) (c/. fluor­escein)9.

11 12 15

* The nom enclature is according to The Chem istry of Carbon Compounds, Edited by E .H . R o d d . V o I . I I I B, p. 1110, Elsevier, New York 1956.

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R. Gopal et al. • Synthesis of Phthaleins 469

The absorption maxima (Amax) of PE (3) given in Table 1, have been found shifted towards longer wave regions (cf. phthaleins).

Experimental

All melting points are uncorrected. The Amax (UV and visible) have been recorded using model DU Beckmann Spectrophotometer in ethanol and IR determined using a Perkin Elmer Infracord.

The phenols have been taken in a little excess of molecular proportion than the acid (1). Cone. H2SO4 (4 — 6 drops) has been used as condensing agent throughout and each dye, when tested, is found free from sulphur.Phenyl resorcinol phthalein (5): A mixture of acid(1) (5 g), resorcinol (5 g) and conc. H2SO4 (4 — 6 drops) was heated at 190°C for 6 hours. The con­densed mass was extracted with 3% NaOH and precipitated with dil. HC1. The precipitate was chro­matographed over silica gel (neutral) with benzene: Chloroform mixture (90:10). The 4th fraction (200 ml) on crystallisation gave deep yellow microcry­stalline dye (6.3 g), m. p. 200 °C. It gave light yellow green fluorescence in ethanol and red colour with green fluorescence in alkali.C20H14O4 Calcd: C 75.47 H 4.4,

Found: C 75.22 H4.12.The preparation of rest of the dyes, given in

Table I was done in identical manner as described in 5 above taking acid and appropriate phenols. (Yield, 60-65% ).

Chromatography of dye (4): On test paper — Whatman No. 1, «-butanol-ammonia was allowed

to run for 13 hours (descending) to give two corres­ponding pink spots (with 1% NaOH) of dye 4 and reference dye phenol-phthalein. (Rp 4, 0.91; phenol- phthalein, 0.93 (/. c.10 Rf 0.92).

Acetylation of dye (5): The dye (5) (1 g), acetic anhydride (15 ml) and fused sodium acetate (2 g) were refluxed at 130 — 140 °C for 3 hours to give co­lourless diacetyl compound (11). It was crystallised from 80% ethanol into microcrystalline substance (1 g), m. p. 1 2 5 °C, soluble in ethanol (Amax 3 2 0 m //, £max- 3 5 6 1 ), acetone and acetic acid.C24H18O6 Calcd: C 71.64 H 4.47 CH3CO 21.39,

Found: C 71.68 H 4.47 CH3CO 21.86.

Bromination of dye (5) — The dye (5) (1 g) was refluxed with 10% solution of bromine in glacial acetic acid (10 ml) at 140 —150 °C for 1 hour to give (1.2 g) shining orange red, dibromo compound (12) (from 80% ethanol), m. p. 225°C, which dissol­ved in ethanol (Amax and £max, at neutral 530 m/u; and 2423 and at pH 7.9, 530 m /u and 4565) with light pink colour and got intensified on addition of NaOH.C2oHi20 4Br2 Calcd: Br 33.58,

Found: Br 34.01.Zink-dust reduction of dye (5) — The dye (5) (2 g)

was refluxed in glacial acetic acid (100 ml) and Zn-dust (5 g) for 20 min to give (1.7 g) glistening colourless crystalline product (13) (from acetic acid in CO 2 atmosphere) m. p. 190 °C , which is acidic in nature and do not give fluorescence in alkaline so­lution.C20H16O4 Calcd: C 7 5 .0 H 5 .0 ,

Found: C 74,62 H 4.75.The acid (13) when left overnight was found

Table I. P reparation, properties and Am»x values of phenyl phthaleins.

Dyes Condensation Dura-

t tion[°C] [h]

m. p.[°C]

Appearance^maxNeu­tra l

(m/x); a t (pH)

£max Found C H

[%]

Calcd. C H

[%]

Phenyl phenol phthalein (4)* 110 6 170 Colourless — 500;1027;550

(12);770

79.12 4.18 79.47 4.63

Phenyl resorcinol phthalein (5)

190 6 200 Deep yellow 480;2385

490 (9.8);7155

75.22 4.12 75.47 4.40

Phenyl catechol phthalein (6)

160 3 177 L ight brown -- 450 (12.2);1971

75.02 4,15 75.47 4.40

Phenyl quinol phthalein (7) 160 3 260 Brown black — 460 (12.5);1710

75.06 4.25 75.47 4.40

Phenyl phloroglucinol phthalein (8)

160 6 250 Orange yellow - 490 (9-5);2488

71.61 3.86 71.85 4.19

Phenyl pyrogallol phthalein (9)

160 6 220 D ark brown 510 (8.8);2572

71.61 3.94 71.85 4.19

Phenyl orcinol phthalein (10) 140 IV2 270 Olive green 490 (12.5);2789

75.58 4.65 75.0 4.82

* Excess phenol, after condensation has been removed by steam distillation.

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470 R. Gopal et al. • Synthesis of Phthaleins

changed to deep yellow compound. This coloured compound and its acetyl derivative were found identical to parent dye (5) and its acetyl derivative(11) confirmed by mixed m. p., Amax-values and superimposable IR.C20H14O4 Calcd: C 75.47 H 4.4,

Found: C 75.69 H 4 .ll.Acetylation of acid (13) — The acid (13) (0.5 g),

acetic anhydride (10 ml) and fused sodium acetate (2 g) were heated in CO2 atmosphere at 130 — 135°C for 3 hours to give diacetyl compound, phenyl dia­cetyl resorcinol phthalin (14). It was crystallised as white crystalline compound (from acetic acid) (0.5g), m. p. 155 °C, which is soluble in acetone, chloroform and ethanol.C24H20O6 Calcd: C 71.28 H 4.95 CH3CO 21.28,

Found: C 70.86 H 4.81 CH3CO 20.98.Potassium, hydroxide fusion of 5: The dye (1 g) with KOH (10 g) was fused for half an hour, cooled and then diluted with 1 1 water. It was extracted with ether (5, 100 ml portions). The extract on crystalli­sation gave resorcinol and the aqueous layer on acidification and then purified precipitated mass resulted acid (1).Excess bromine treatment on 5: The dye (5) (1 g) was refluxed with a solution of 5 g of bromine in 10 ml of glacial acetic acid for 1 hour at 140 °C. It was cooled diluted with water (100 ml) and separated on silica gel column by eluting with alcohol; benzene (30:70). The first band was obtained, which on recrystallisa­tion gave acid (1) while the second band gave sym- tribromoresorcinol (confirmed by mixed m. p., and superimposable IR).

Red resorcinol phthalein (15): The dye (5; yellow form) (0.5 g) was dissolved in aqueous NaOH (10%, 20 ml) heated to boiling with steam and precipitated with a slight excess of boiling HC1 to give bright red substance (15), which was also obtained by boiling the respective yellow form with a large quantity of water containing a little HC1. It was washed several times with boiling water, dried over P 2O5 under vacuum for 24 hours (0.5 g), melted at 190°C. The yellow form is reobtained by the addition of acid to a cold alkaline solution of red form (15).C2oHi4 0 4 Calcd: C 75.47 H 4.4,

Found: C 75.31 H 4.24.The authors express their thanks to Dr. J. D.

T e w a r i for his useful suggestions. A grant and fellowship (to R. G.) from C. S. I. R., New Delhi is greatfully acknowledged.

1 M . S. N e w m a n and C .D . M cC l e a r y , J . Amer. chem. Soc. 63, 1537 [1941]; idem ibid. 67, 254 [1945].

2 M .S . N e w m a n and C.W. M u t h , J . Amer. chem. Soc. 73, 4627 [1951].

3 C. G r a e b e , Chem. Ber. 33, 2027 [1900].4 R.C. M a r t i n , J. Amer. chem. Soc. 38, 1142 [1916].5 F . U l l m a n n , A n n . 17, 291 [1896].6 H . B u r t o n a n d D .A . M u n d a y , Chem. Ind. 1956,316;

idem., J. chem. Soc. [London] 1957, 1727.7 P .M . M a g i n n i t y and T .I . G a i r , J . Amer. chem.

Soc. 74, 4958 [1952],8 M .H . H u b a c h e r , J . Amer. chem. Soc. 65, 1655

[1943].9 W. R. O r n d r o f f and A. J. H e m m e r , J. Amer.

chem. Soc. 49, 1272 [1927].10 L . H o u g h , J . chem. Soc. [London] 1949, 2511;

M. L e d e r e r , Science 112, 404 [1950].

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