Sciencemadness Discussion Board

BzOH + HNO3 --> ?

hodges - 1-9-2009 at 14:36

I recently obtained some benzyl alcohol. I was doing some experiments that involved HNO3, so thought I would oxidize some of the BzOH. Supposedly BzO is the result. So I took about 1ml of BzOH in a test tube and added about 0.5ml of 70% HNO3. This resulted in an immediate runaway reaction, as could be expected. However, I don't think the product was BzO. The product formed a yellow lower layer. When I washed it with water, it turned the water dark yellow. And it didn't smell like cherries - it was more like shoe polish or varnish. So I'm wondering what product(s) I ended up with. I'm thinking either benzyl nitrate or nitrobenzene, based on my limited knowledge of organic chemistry.


DJF90 - 1-9-2009 at 15:03

BzOH is not benzyl alcohol. Bz is the benzoyl group, BzCl is benzoyl chloride, BzOH is benzoic acid. Bn is the abbreviation for benzyl. Therefore benzyl alcohol is BnOH, but benzaldehyde would be BzH (If I havent made a mistake here). /rant.

I'm guessing you tried oxidising benzyl alcohol with nitric acid, expecting to get benzaldehyde but did not? Its possible you got ring nitration, as the ring should be about as active as in toluene. Nitrobenzene would require a C-C cleavage, so I'm gonna write this off atm. It is also an option that you oxidised the alcohol AND nitrated the ring. I cant really comment more than that at this late hour.

JohnWW - 1-9-2009 at 15:11

To nitrate the benzyl alcohol would normally require probably an higher concentration of HNO3, plus a small amount of H2SO4 to catalyze it and bond some of the water produced. So I think the major product of your reaction would be most likely the nitrate ester, benzyl nitrate, rather than a nitro-compound (which if occurring would probably be primarily the meta-isomer, as with the nitration of benzoic acid), except as a minor side-reaction which may have imparted the yellow tinge. Benzaldehyde is not yellow, and it has a characteristic smell. However, in view of the fact that phenol, a somewhat similarly polar aromatic compound, undergoes nitration (although firstly ortho- and then para-, instead of meta-, unlike benzoic acid and probably benzyl alcohol) with even dilute HNO3, but accompanied by some oxidation of the ring, the extent of ring nitration may be quite substantial, and there may be ring-oxidation byproducts.

[Edited on 2-9-09 by JohnWW]

DJF90 - 1-9-2009 at 16:43

I dont see where you're getting meta nitration from John - only ortho and para positions are activated.

S.C. Wack - 1-9-2009 at 18:52

Dilute, yellow acid should work better for benzaldehyde. Though not fast or at room temp.

Typical nitration, of benzaldehyde, giving o- and mostly m-nitrobenzaldehyde in high yield, is well known.

[Edited on 2-9-2009 by S.C. Wack]

smuv - 1-9-2009 at 20:52

Yes probably the ester; formation of nitrate esters is exothermic.

Burn the oil (in the absence of any colorful ions such as sodium, potassium or copper), if it burns with a white/grey flame it is definitely the nitrate ester.