Benzyl Cyanide or BnCN is the type of organic compound which is made by the reaction of benzyl chloride and sodium cyanide. Benzyl cyanide has the chemical formula C6H5CH2CN. This compound is toxic, colorless (sometimes pale yellow) and oily.
Benzyl cyanide is also included in the aromatic liquid compound category. The main use of benzyl cyanide is as precursor to varied compounds, both useful and even dangerous compound in organic chemistry. You can see benzyl uses in some fields including production of chemicals like phenobarbital, methylphenidate, and some other amphetamines.
This chemical compound has the category of U.S. DEA List I chemical in the United States. Other uses of benzyl cyanide is for the making of methadone, pethidine and ketobemidone. Aside from its uses in certain chemical production, benzyl cyanide is also useful for other applications like organic synthesis of dyes, perfume, pesticides and pharmaceuticals. You can find the important uses of benzyl cyanide in as the penicillin precursors.
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Chemical Properties of Benzyl Cyanide
As mentioned before, benzyl cyanide has the chemical formula C6H5CH2CN. Benzyl cyanide is considered as the aromatic liquid chemical compound type. It has the molar mass of 117.15 g/mol and density of 1.015 g/cm3 . The melting point of benzyl cyanide is −24 °C or 249 K. While the boiling point of this compound is 233 to 234 °C or 506 to 507 K. The characteristic of this compound is colorless, toxic content and oily form. In the chemical reaction, benzyl cyanide can be used in the hydrolysis reaction and pinner reaction.
In the hydrolysis reaction, benzyl cyanide can yield phenylacetic acid. While using the pinner reaction, benxyl cyanide is able to produce phenylacetic acid esters. The benzyl cyanide compound can also form an active methylene unit on the carbon between the aromatic ring and the nitrilefunctional group. The active carbon named nitrile anion is a great reactive intermediate in the making of new carbon carbon bonds.
As an alternative, you can prepare benzyl cyanide with the alcohol potassium cyanide and benzyl chloride. But the normal sodium cyanide is actually cheaper than the potassium cyanide and it can create the great result, so this compound is more preferable.
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We’ve already known that the main benzyl cyanide uses are as the great intermediate for some different chemical compounds. Benzyl cyanide is able to produce some useful and dangerous chemical compound. The popular uses of this colorless compound is for the making of methylphenidate, phenobarbital, and other amphetamines. Benzyl cyanide can be used as the starting material and as solvent in the fungicides’ synthesis process, antibiotics and some pharmaceutical purposes. Benzyl cyanide is also important in fragrances production which is used to produce phenethyl alcohol. The partial hydrolysis reaction of benzyl cyanide can make the anticonvulsant ot 2-phenylacetamide.
Also read: Types of Cyanide
In the pharmaceutical industries, benzyl cyanide has the broad uses as a precursor for some popular pharmaceutical products. Some of the benzyl cyanide uses in the pharmaceutical field are as follow:
- In Anorectics, as an example in production of sibutramine
- In production of analgesics, including ethoheptazine, ketobemidone, pethidine, and phenoperidine
- In making of Antiarrhythmics like disopyramide and others
- In the Antidepressants production
- In production of Antihistamines, such as levocabastine and chlorphenamine
- Used in the production of antimalarial medications, like pyrimethamine
- For antitussives such as isoaminile, oxeladin, butethamate, pentapiperide, pentoxyverine and some more
- For Diuretics, like triamterene
- For Hypnotics cure like alonimid and phenobarbital
- For production of Spasmolytics, including pentapiperide and drofenine
- For stimulants like methylphenidate
- For Azatadine production
In the preparation of benzyl cyanide, you must take following points into account. These points have strong relation with the characteristic of benzyl cyanide both chemically and physically. So here’re some notes you should take when doing preparation of benzyl cyanide:
1. The Purity Benzyl Cyanide
The quality of benzyl chloride significantly gives impact to the quality of benzyl cyanide. The better benzyl chloride used, the more pure benzyl cyanide which will be produced. If you use the low quality benzyl chloride, you will get only 60 to 75 percent purity of benzyl cyanide. You shall use the good quality of benzyl chloride to produce at least 85 percent purity of benzyl cyanide. Technically, benzyl chloride will yield on the distillation at 8 percent of high boiling material. The benzyl chloride which boils over 10 degree will create the better purity of benzyl cyanide.
2. Distill Benzyl Cyanide
In the preparation process, it’s better to distil off the alcohol’s ;ast portion and water. It’s also advisable to distil the benzyl cyanide in the lower pressure. We know that technically white solid will separate invariably during the distillation in the normal pressure level. So it’s better to use lower pressure to distill benzyl cyanide to avoid such a risk.
3. Steam Distillation
One of the method to purify the benzyl cyanide is by steaming distil the benzyl cyanide after you distill the alcohol firstly from its reaction mixture. If you do it in the normal pressure level, the steam distillation process will be very slow. In addition, if you use the normal condenser, it will require about 18 to 20 hours to remove all the unstable products from 500 gram of benzyl chloride material. The distillation process is separated in two layers.
First, you do remove the benzyl cyanide layer then do distillation of this compound. If you use this method, you will get the better benzyl cyanide product which is more pure. You will also not get any residual material. After you remove the excess of the benzyl chloride, you just have to boil it in the constant temperature level. However, this type of steam distillation is not really advisable to operate in the laboratory.
4. Mix This Compound with the Sulfuric Acid
If you do the preparation of benzyl cyanide with the above considerations, you can actually get the great benzyl cyanide product which meets the standard as the precursor material for certain chemical products like phenylacetic acid and ester. Meanwhile, if you this kind of procedure, you may experience the unpleasant smell due to the existence of benzyl isocyanide. This process also can make color on the standing. To avoid this risk, you can do the following method which is advised by John R. Johnson.
So, when you have done distilling the benzyl cyanide, you can mix this compound with the sulfuric acid. You must use the warm (about 60 degree) sulfuric acid having 50 percent purity. To have this 50 percent sulfuric acid, you can mix 275 cc of pure sulfuric acid to the 500 cc of the water. You can shake the mix of benzyl cyanide and sulfuric acid for about five minutes. You can separate and wash the benzyl cyanide with the saturated sodium bicarbonate solution in the equal volume.
After it, you shall add the equal volume of half saturated sodium chloride solution. Then, you have to do drying and distillation in the lower pressure level. The loss produced in the washing process is really low so you can neglect it. By using this method, you will remove the isocyanide and create white product. There will be no color appeared on the standing.
Preparation of Benzyl Cyanide
There are different ways to create benzyl cyanide compound. The popular one is through Kolbe nitrile synthesis. This kind of chemical reaction uses benzyl chloride and sodium cyanide to create benzyl cyanide. Another way is by conducting oxidative decarboxylation reaction. To make benzyl cyanide, you must do oxidative decarboxylation process to phenylalanine.
To prepare benzyl cyanide, you need 500 gram or 10 miles of sodium cyanide powder and 450 cc of water. The sodium cyanide powder must have at least 96 to 98 percent purity. You should warm this mix in the water bath to dissolve the sodium cyanide. After it, you mix the 1 kg or 8 moled of benzyl chloride with the 1 kig of alcohol in separatory funnel. The benzyl chloride must have temperature of 170 to 180 degree while the alcohol should have at least 95 percent purity. You must do this mix for one half to three quarters of 1 hour. After it, you heat this mix up in the reflux condenser on the steam bath for about 4 hours.
Then, you should cool and filter it to remove the sodium chloride material. You can wash the salt which has been filtered with the little amount of alcohol to remove the residual benzyl cyanide. You then have to palce the flask in the conesnser. In this process, you should distill alcohol in the steam bath. Then, you do cool the residual liquid and filter it if it’s necessary. Now, you will have the separated benzyl cyanide in the claisen distilling flask. You can distill it in the lower pressure and then you will have the benzyl cyanide product.
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Safety and Regulation
Even though benzyl cyanide has many uses in different fields, we can’t neglect the fact that this compound contains toxic and may create dangerous effect. Benzyl cyanide can also be used as the precursor for the dangerous chemical compounds. Up to this fact, many countries create the special law to regulate the benzyl cyanide uses. In United States, benzyl cyanide is classified as the DEA List I Chemical. Talking about the safety of benzyl cyanide, this compound can create serious effect to human.
Benzyl cyanide is the irritant for human skin and eyes. We know that all the derivatives of benzyl must have this potential risk. Benzyl cyanide is toxic and has probability to make poison. If you burn this compound, benzyl cyanide can create the hydrogen cyanide which can kill a person.
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