Benzil dioxime

Hello science madness comunity

I attempted to prepare benzil dioxime following the procedure from this paper https://doi.org/10.1139/v75-043
I obtained a good amount white precipitate. I initially measured its m.p and it was 241-245 c°. Then I filtered it off, washed with methanol several times and then with hot water. When the precipitate dried I measured its melting point again and it was 250-251C°. But the IR spectrum of the precipitate was not satisfying. Do you have any thoughts? Can anyone provide me with a method to successfully prepare benzil dioxime?

Thank you



[Edited on 28-5-2021 by Knowledge Seeker]

Quote:

Literature References: Three isomers occur: a or anti, b or syn, g or amphi. Prepn of a-form from benzil and hydroxylamine hydrochloride: Brady, Perry, J. Chem. Soc. 127, 2874 (1925); F. J. Welcher, Organic Analytical Reagents vol. III (Van Nostrand, New York, 1947) pp 224-227; Boyer et al., J. Am. Chem. Soc. 77, 5688 (1955). Prepn of b-form: Brady, Perry, loc. cit.; Boyer et al., loc. cit. Prepn of g-form: Welcher, loc. cit., pp 227-228; see also Boyer et al., loc. cit. Derivative Type: a-Form Properties: Crystals from methanol, mp 238-240°, Boyer et al., loc. cit., also reported as mp 243-244°, Meisenheimer, Lamparter, Ber. 57, 276 (1924). Practically insol in water, ether, glacial acetic acid; slightly sol in alc; readily sol in NaOH solns. Melting point: mp 238-240°; mp 243-244°, Meisenheimer, Lamparter, Ber. 57, 276 (1924) Derivative Type: b-Form Properties: Crystals, mp 212-214°, Meisenheimer, Lamparter, loc. cit. Melting point: mp 212-214°, Meisenheimer, Lamparter, loc. cit

Quote: Originally posted by Boffis

.....so maybe you have a mixture of di and mono oximes.

Quote: Originally posted by Fery

Does benzil dioxime have any advantage than more common dimethylglyoxime?

Hi Boffis. My suggestion is based only on m.p. determination.
But if Knowledge Seeker's determinations of m.p. are incorrect, giving values higher than in reality, with error about + 5 C, then it changes everything.
IR spectra for the dioxime (and also for oxoanilide) are available from internet, but differs markedly from the pictures above.
I have impression that KS's IR masurement is not done correctly
Nevermind.
I have some benzil, prepared long time ago. I am going to try this preparation if I have time. As Boffis noticed, orginal procedure utilizes hydroxylamine hydrochloride alone, who knows why....
Besides the yield of the dioxime is very low, comparing to input diketone. The author couldn't afford sodium acetate, the reaction needs higly acidic medium, or what ?
Fortunately, all substrates (but time) I have at hand

Quote: Originally posted by kmno4

As Boffis noticed, orginal procedure utilizes hydroxylamine hydrochloride alone, who knows why....

reactants:
benzil 2,10 g (10 mmol, Molar mass 210.232 g/mol)
hydoxylamine hydrochloride 1,80 g (26 mmol, 1,3 fold excess, Molar mass 69.49 g/mol)
7,5 g methanol (should be 9,5 ml, I almost always weigh liquids instead measuring their volume)

procedure:
Reactants were added into 50 ml RBF and rfx for 4 hours in oil bath T 90-100 C, in the beginning gently swirling the flask so in 15 minutes all hydroxylamine hydrochloride dissolved and bubbles of boiling disappeared (no solids present, methanol boils silently without bubbling because of its low b.p.).
After 2 hours there was again a solid present in the reaction (this is now the product) and the boiling bubbles observed again.
After 4 hours of reflux the reaction was cooled down to room temperature and then to +4 C (outside, winter temperature) for few hours.
Solid product sucked on cold sintered glass outside (+4 C winter temperature).
Washed 2 times with 10 ml cold water, the product a little sticky on sinter.
Washed 2 times with 5 ml of 50% methanol : water, the product nice crystalline, the stickiness lost on the first washing already.
Air dried for 1 day, during 1st half a day the weight loss was 0,04 g, during second half a day the weight stable.
Yield 0,59 g 24,5% (2,45 mmol, Molar mass 240,26 g/mol)

Original method suggests 3 hours reflux but in my experiment it seemed that at the end of 3rd hour more and more of the product was crystallized in the flask so I decided to prolong the reflux by an extra hour from 3 to 4 hours totally. Maybe it should be investigated whether it was only my false feeling or whether it is worth to do it to improve yield. My goal was just to prepare a little of this Niclon indicator and create a color complex with Ni2+
I do not know whether stirring or boiling chips are necessary, I did only little of sporadic manual swirling at the beginning and did not use boiling chips (in the middle of reaction methanol boiled smoothly and at the end there was again solid product present which facilitated boiling).
No escaping HCl observed.
Top of condenser was loosely closed with a stopper to prevent entering unnecessary air and thus moisture and allowing back reaction hydrolysis (original method does not do it, but by my opinion the less water then less back hydrolysis of the oxime to ketone in HCl environment - I already hydrolysed oxime to carvone in even less acidic environment in quite diluted oxalic acid in water).
Another method with much more complicated derivate used 3 fold excess of hydroxylamine hydrochloride with anhydrous K2CO3 and 80 hours reflux (1 mmol substrate + 6 mmol hydroxylamine hydrochloride + 3 mmol K2CO3) - see the attached file IJCB 38B(10) 1208-1210.pdf
Unlike yellow reactant benzil the product diphenylglyoxime is white. Maybe the methanolic mother liquor could be further reacted with extra hydroxylamine and K2CO3 to produce more of the desired product?

some links:

I could buy this Niclon indicator for 10 EUR per 10 g but then there is less fun, isn't it?
https://aukro.cz/indikator-niklon-p-a-diphenylglyoxime-c14h1...



https://sci-hub.ee/10.1139/v75-043

copy/pasted useful information:
A 0.02% alcohol or acetone solution of
a-benzildioxime which has been made somewhat amoniacal
will immediately produce a copious intensely red precipitate
of C2 H22N4O4Ni with a solution containing
0.002 mg. nickel in 5 cc. (~ part in 2,000,000). Ten
cc. of an ammoniacal solution containing 1 part per
1,000,000 of nickel and 100 times that amount of
cobalt gives a distinct and immediate test for nickel.
Iron, silver, magnesium, chromium, and manganese do not
interfere with the qualitative determination. Large
amounts of nitrates seriously affect the determination
and must be removed by evaporating with sulfuric acid
before adding the reagent. In the quantitative determinations
amounts containing less than 0.025 g. nickel
should be used. A slight excess of a warm solution of
the reagent in alcohol, to which ammonia has been
added, is added with stirring to the ammoniacal nickel
solution and warmed for a few moments on the water
bath.

Attachment: IJCB 38B(10) 1208-1210.pdf (597kB)
This file has been downloaded 177 times

Attachment: v75-043.pdf (177kB)
This file has been downloaded 171 times



now photos:


reactants, note the pale yellow color of benzil





reactants in the flask and putting the flask into oil bath





methanol boiled with bubbles only at the beginning (first 15 minutes) until hydroxylamine hydrochloride dissolved completely and also for the last 2 hours when the product crystallized out





after 4 hours the reflux was done, white crystals of product visible, on cooling down more crystals formed especially on the surface which then sank to the bottom





after cooling down the product was sucked on sinter, washed with water and 1:1 methanol:water





air dried product, note the white color unlike pale yellow reactant





complex with Ni2+ very very very diluted, the indicator was dissolved in warm methanol, in the attached file v75-043.pdf they used dimethylsulfoxide as a solvent