05-26-04 10:02
No 509703
Elementary wanted to know about transforming cinnamic acid to phenylacetaldehyde: Post 304573 (Elementary: "Cinnamic Acid 2 Phenylacetaldehyde", Chemistry Discourse).
While browsing through a series of monographs on named reactions today, I came across an interesting application of the Hoffman reaction. Unfortunately I was in a hurry and had time only to scribble down an abbreviated account of the synthesis. Better documentation can be looked up later if desired.
(prep of NaOCl soln) 55 grams of Cl2 is passed into 150 cc of water mixed with 600 grams of cracked ice and 100 g NaOH. Water is added to make up 1 liter of solution.
14.7 g cinnamic amide in 125 cc of MeOH is combined with 130 cc of the above NaOCl soln and warmed on a water bath. A thick sludge of crystals soon forms. The mixture is rapidly cooled, filtered, and the crystals washed with dilute EtOH and water. Yield: 13 g (70%) methyl styrylcarbamate.
25 grams methyl styrylcarbamate is dissolved in 100 cc warm ethanol, and to this soln. is added gradually 48 cc of 6 N sulfuric acid. CO2 evolves, some urethan precipitates but redissolves on heating. When all H2SO4 has been added, the formed phenylacetaldehyde is immediately steam-distilled.
The yield of phenylacetaldehyde is described only as "good."
Two questions spring to mind: is simply exposing cinnamaldehyde to the air for extended periods an acceptable way of preparing cinnamic acid (followed by some purification)? And is cinnamic amide formed like one would form (say) acetamide from acetic acid? If the transformation of cinnamic acid to cinnamic amide is not straightforward then I have not really answered Elementary, I suppose.
19th century digital boy
(Chief Bee)
05-26-04 15:34
No 509735
Related: according to the J. Chem. Soc. article in Post 509078 (Rhodium: "Ketones from Halohydrins (from alkenes)", Novel Discourse) phenylacetaldehyde can be made by decarboxylating the bromohydrin gotten in 90%+ yield by treating cinnamic acid with bromine water. Their reference for the decarboxylation is J. Chem. Soc. 119, 1775 (1921)
The Hive - Clandestine Chemists Without Borders
(Hive Addict)
05-26-04 17:41
No 509746
Presuming the PhAcH is meant to be a precursor to PAA, this might be interesting:
Phenylacetic acid by oxidation of cinnamaldehyde w/ oxone; 1h ; 2°C ; in H2O / acetone ; 40% yield.
Tetrahedron; 54,3-4.1998; 401 - 410 .
--psyloxy--
(Chief Bee)
05-26-04 20:12
No 509760
(Rated as: good read)
Oxidation of aldehydes with OxoneŽ in aqueous acetone
Kevin S. Webb and Stephen J. Ruszkay
Tetrahedron 54(3-4), 401-410 (1998)
Abstract
Several aldehydes have been converted to the corresponding acids in good to excellent yields. The oxidant was OxoneŽ (potassium peroxymonosulfate), the reactions were performed in either 20% aqueous acetone, water, or aqueous acetonitrile, and buffered with sodium bicarbonate.
The Hive - Clandestine Chemists Without Borders
(Fragile ego)
06-02-04 02:55
No 510793
The above article also has a nice procedure for p-methoxybenzaldehyde to p-Methoxyphenol, using Oxone. A roundabout otc way to the 2C's/DO's.
http://www.democracynow.org/ - The Exception to the Rulers