Benzaldehyde from benzyl alcohol

Bushroot · Fri Aug 26, 2005 2:43 pm

I found the following metod most convinient (without expensive DMSO) :

In the apparatus for distillation with addition funnel instead of thermometer is placed 90 grams of K2Cr2O7 and 350 ml of water. The mixture is brought to boiling and 35 ml of benzyl alcohol is added dropwise with a moderate speed. The forming benzaldehyde immidiatelly distills with water steam. Yield 28g of absolutely pure BzCHO (83%)

Vitriodor · Sat Aug 27, 2005 4:34 am

In what climate do you live? Phenol is solid below 41 C, at least if it is pure. Did you melt it or was some water added. The presence of a little bit of water can lead to liquified phenol. And in this way your yield of 83% is more likely to be correct.

Bushroot · Sat Aug 27, 2005 3:08 pm

umm sorry Vitrodor maybe you confused the Benzyl alcohol (C6H5-CH2-OH) with phenol (C6H5-OH) ? Benzyl alcohol is a goo-liquid at room temp. That reaction above can't be done with phenol

But as for phenol, it surely is solid in my climate, im from Moscow

java · Consumer

bushroot.....do you have any references for your method? , and have you had your stuff tested to see if indeed is benzaldehyde?............java
Here are some comments and discussion on the subject found over at sciencemadness....

https://sciencemadness.org/talk/viewthread.php?tid=55

also,

Bushroot · Sun Aug 28, 2005 4:59 pm

Yes, this is benzaldehyde indeed. The distillate (heavy translusent oil) after steam distillation smelled cherry's stones (bitter almond they say but I never sniffed real bitter almond). Distillate was extracted with ethylacetate and gave a full flask of snow white precipitate after night standing with 30g of Na2S2O5 in 50mls of water.

The method is based on process of making ethanal (acetaldehyde) from ethanol which is almost in any org synthesys study-book (praktikum, dunno the proper english word).

java IMHO your method is a bit too complicated (H2O2 is deficit for me) for this simple procedure. You should try mine and I believe you won't regret Smile

Vibrata_Lumine · Fri Sep 16, 2005 8:56 am

Swis once found very pure Ba WIth a Microwave MNO2 is DOped onto silica 5%W/W By adding KmNo4 To Silica gel in Isopropanol. The reactino produces heat so go slow. The IPA Oxidises to acetone As the MnO2 Percipitates onto the silica.. This is then filtered and the filtercake dried in the oven at 25 till bone dry. Then just add the BZOH to the Doped silica and heat in the microwave in 15 sec bursts till the rxn is complete follow with TLC till you gett the time down. Then just filter and distill. There is a ref for this on rhodiums pg. It is an awesome rxn. Microwaves are magic the rxn takes less than 10 mins and you don't have to worry too much about overoxidising due to the low heat and short rxn time. A little DCM aids in the filtration The product is very pure

loki · guinea pig

there's a really simple microwave synth for benzyl alcohol-->benzaldehyde. i like this route, personally, it is very easy to get benzyl alcohol from any benzylic halide after a bleach/HCl chlorination by hydrolysing with NaOH or NaCO3

the synth involves adsorbing activated manganese dioxide onto silica and then irradiating for 5 minutes and the yield is like 90% or something.

oh... u stole my thunder vibrata_lumine Very Happy

oops...

well i did add the thing about how to go from benzyl chloride/benzal chloride to benzyl alcohol via base hydrolysis Very Happy

the method you describe using potassium permanganate is one way to do it, manganese dioxide that has been treated with sulphuric acid will provide the desired active manganese oxidiser too. (manganese dioxide is used to make black glazes and is very cheap).

activated manganese sulphate in this form can perform the oxidation directly from toluene tho, and can be regenerated with electrolysis.

i personally think that going via benzyl alcohol is easier and better yield, the conversion of toluene to benzyl alcohol via chlorination/hydrolysis runs to something like 80% yield which is very nice considering how cheap the precursor is, and the reagents too (bleach, pool acid, pH up). the microwave reaction's yield is very attractive, the manganese oxidation direct to benzaldehyde is either equal or lower in yield than the combined chlorination/hydrolysis/mw oxidation route.

the fact that potassium permanganate can be used as well is very nice tho, although its a bit tricky to get it *is* available.