Sciencemadness Discussion Board - Unexpected reaction with benzaldehyde solution.

Unexpected reaction with benzaldehyde solution.

CaptainMolo - 24-8-2017 at 07:24

I have a small mystery on my hands, I attempted this earlier this week to see how much benzaldehyde was in a brand of artificial almond flavoring that is easily available to me.

The flavoring is a mixture of about 36% ethyl alcohol, water, and benzaldehyde.

The stuff is so cheap I was mainly just playing around with some concepts to see what would happen, so I took a two ounce bottle of the stuff and put it in a separatory funnel and attempted to create a bilayer system by altering the aqueous solution.

I added some sodium bicarbonate to the liquid, and immediately some fizzing occurred, which presumably was carbon dioxide. I wasn't expecting a reaction at all, so much as I was hoping that the change in pH would force the alcohol/benzaldehyde into a separate layer. Similar to the process of salting alcohol out using sodium carbonate.

I could have made sodium carbonate from my bicarbonate, but I was being lazy and I was also curious if it could be done with bicarbonate.

A white precipitate formed, so I filtered this off with a vacuum filter and saved it. It has no discernible scent, and insoluble in water, or at least so sparingly so that most of it didn't remain in solution.

The mother solution also no longer had a strong scent of benzaldehyde, which leads me to believe that it must have reacted to form the precipitate.

I think it's Benzoic Acid, but I haven't done any further tests on it as of yet.

I know that forming the bisulfite adduct is an easy and clean way to sequester the benzaldehyde, but like I said this is not really about performing a well known procedure, but more about trying stuff out.

Any ideas?

Melgar - 24-8-2017 at 10:15

Probably citric acid, and/or ascorbic acid as an antioxidant. There's probably at least some sort of cheap antioxidant in it to prolong its shelf life, and it's hard to get much cheaper than ascorbic acid. And aldehyde-type flavorings like vanillin and benzaldehyde taste really weird without a slightly acidic pH.

You can test to see if it's benzoic acid by dissolving the sodium salt in water, then acidifying it with virtually any water-soluble acid. If it starts forming this insoluble scummy stuff that floats to the top, but doesn't form a liquid layer, then that's a sign it could be benzoic acid, at least partially.

You're probably aware that you're not going to be able to get a usable amount of benzaldehyde that way, and you'd have better luck with benzyl alcohol or even toluene, but it's an interesting and inexpensive way to use chemistry to elucidate the content of mysterious compositions, so keep up the good work!

CaptainMolo - 24-8-2017 at 11:21

Thanks! Yes I am aware that the concentration is likely very small and determining the components was exactly my goal. Your explanation really clears things up and I will try what you suggested to determine the composition of the precipitate. Part of the mystery was that the amount of precipitate seemed very large compared to my expectation of the benzaldehyde content.

I'll post any further information I am able to gather for those that are curious.

For future experimentation I did actually order some benzyl alcohol and I'm planning to synthesize benzaldehyde from it via the nitric acid oxidation method I read about on here a while back, so it's kind of funny you mentioned that.

Thanks again!

Corrosive Joeseph - 24-8-2017 at 13:49

Most paint strippers are loaded with benzyl alcohol these days......... Something had to replace DCM after it was demonized

Chemplayer has a youTube video on MnO2 oxidation - https://www.youtube.com/watch?v=HrZAMlj0kPM

This is readily available from batteries and pottery suppliers (albeit in varying degrees of purity)

I haven't done it but I hear it works a treat........... Even using an excess of impure oxidant

/CJ

[Edited on 24-8-2017 by Corrosive Joeseph]

CaptainMolo - 25-8-2017 at 08:06

Thanks for the tips!

I haven't seen any Benzyl Alcohol based strippers in my area yet. From what all I've found lately, it's all DCM and Methanol. I will likely be distilling some of this in the near future for both of these components though.

wg48 - 25-8-2017 at 09:24

Quote: Originally posted by Melgar

snip
And aldehyde-type flavorings like vanillin and benzaldehyde taste really weird without a slightly acidic pH.
snip

Is that a personal observation or do you have a reference for it?

I am interested in that as I use vanillin to flavour drinks such as coffee, milk and strawberry smoothies. I have found using dried milk to make a milk drink if I add a pinch of bicarbonate it improves the flavour. In fruit smoothies (presumable acidic) the vanillin does not seem to work for my palette. I am guessing but I would expect its the smell of the vanillin that is detected which may be independent of the ph of the drink. But then flavour is a combination of smell, taste and a function of personnel preferences.

Melgar - 25-8-2017 at 12:10

Quote: Originally posted by wg48

Very few foods have a basic pH. Even milk is slightly acidic, thanks to lactic acid. Coffee is definitely acidic, and so are strawberries. Granted, the pH of milk is only slightly below neutral, but our taste buds are pretty sensitive for picking up stuff like that.

If you think about it, it's evolutionarily advantageous to prefer acidic food over alkaline food, since most of the acids that are common in food, like citric acid, acetic acid, and lactic acid, can be metabolized for energy.

CaptainMolo - 26-8-2017 at 06:46

Quote:

If you think about it, it's evolutionarily advantageous to prefer acidic food over alkaline food, since most of the acids that are common in food, like citric acid, acetic acid, and lactic acid, can be metabolized for energy.

I don't know if I have ever eaten a legitimately alkaline food, thinking off the top of my head. I'm curious now, what's a common food that's alkaline? And I don't mean something that's added to food like sodium bicarbonate. I for some reason can't think of one.

Also can anyone suggest a flavoring or scent molecule that one could synthesize easily from benzaldehyde that is significantly different than the parent compound? I was thinking it would most likely need to be an ester of some sort.

Back to the original discussion, I haven't had a chance to play around with my mystery solid much yet, because currently I am trying to solve my heating problems, however I did check on it and it's completely dry now in it's little dish. When it dried it formed a cake, and is very crumbly/powdery when disturbed.

I read for a while about possible side reactions and decided it was safe enough to taste test it to see if it was simply undissolved sodium bicarbonate or something identifiable. It was very reminiscent of sand, or titanium dioxide. Pasty when wet and with no discernible flavor, slightly abrasive, and mostly insoluble in saliva.

Considering that I am currently typing this reply, I would say that my assessment of the taste test safety was accurate enough for all practical purposes.

[EDIT: Moved hotplate problem description to Apparatus section]

P.S. Seeing as this thread appears to be developing several concurrent discussions, would it be more appropriate for me to post these other questions in other topic areas, or is this okay when it's infrequent? I don't want to break the rules of the forum etiquette.

-Captain Molo

[Edited on 26-8-2017 by CaptainMolo]

Melgar - 26-8-2017 at 08:01

I bet your salt is sodium phosphate. That would make sense, since phosphoric acid is often used as a pH buffer in food.

As for the rest, it should probably go in the Reagents and Apparatus forum.

CaptainMolo - 26-8-2017 at 08:48

Quote: Originally posted by Melgar

I bet your salt is sodium phosphate. That would make sense, since phosphoric acid is often used as a pH buffer in food.

As for the rest, it should probably go in the Reagents and Apparatus forum.

See I knew someone would figure it out! I had no idea there was phosphoric acid in that flavoring. It makes sense that they would use phosphoric acid since it's very stable and relatively neutral sour flavored, and it's readily available. Heck they put phosphoric acid in coke and I don't think you can tell the difference with it or with ascorbic acid substituted for instance. How cool. I'm not sure what I could conceivably use sodium phosphate for, so I'll probably dispose of it, but I'm glad the mystery is solved.

I'll edit my post and move that content to the apparatus section as suggested.

Thank you!