1701.
> C1 > Br > I . Therefore, this should be the series for an increasing hydroxyl interaction with the ring since such effects are partially mutually exclusive. As a consequence, resonance interaction probably constrains the 0-H bond direction to the aromatic plane t o the least extent in ofluorophenol and to the greatest extent in o-iodophenol.Y
l&O.=-J- 6+
80
6-
-__ 6i s e t en xreater t h a n t h e c~iiniiaralileinteraction shown by the Auoro jirouli T h i s again would decrease t h e stability of t h e t i ' a i i s 0 - € 1 posi-
tion On the other hanil. this t y p e u f resonance interaction is less i m p o r t a n t for sulfur t h a n f < J rr,xygen because of t h e greater dilficulty in forming T I ) tiimd\, b u t xgiiin tlie 0-H band is single. T h i s is pruhably d u e to t h e much xreilter strength of t h e 0-13. . . S hydrogen hond as evidenced b y a i u shift uf a h o u t 150 c m . -I; A . \Ir. B a k e r , J . P h y s . C h e w . , 62, T41 :1'328)
( 8 ) FIX phenols having a n o-alkoxy g r o u p a single 0-H band is ohser\.ed which has a A P shift of a b o u t 55 cm. - 1 f r o m t h e phenol porit i o n . T h i s is compatible w i t h t h e above explanation because t h e alkoxy interaction of t h e t y p e
PITTSBURG, CALIF.
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Mechanism of Chromic Acid Oxidations. Part IV. Oxidation of Formaldehyde by Chromic Acid HI.A.C . C I I ~ T T E RAJNI D S.UIIRKIX.IK ~ I ~ ~ I < I I E K J I ~ : I ; KECEITEI)
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,I kinetic study of the oxidation of formaldehyde with chromic :tcid h a 5 bceii riiarlcl. The circler o f t h e reaction \ritli respcct to cliriimic acid, forInaldehyde and H + ion has been found to be first, first :inti s,ecinid at all hydrogen ion ciincentr:itioiis. The teinperature coefficients for t h e temperature range between 25 and 55' :it v:irious concentrations have been tieterininetl. The product of the reaction, formic acid, x i s detected by the chrornotri~picacid reaction and then estimated by c ~ ) r i d u c t ( ~ ~ n etitration. tric The effects of light is negligible. The effects of siirne salts ( i n the oxidation rates have heen itudicti. Tlic induction factor for the induced oxidation of iiicriiganous sulfate til in:ing:iiiese dioxide has been found to he 0 , t 7 , Frilin ;i knowletigc of tlic above results :i prissible incchatiisrn for tlic ositl:itiiin rlf iorrnuldehyde bl- chromic acid has hccn pr~il)iiicd
Introduction
A survey oi the literature reveals that although a large number of oxidizing agents have been used to oxidize aliphatic as well as aromatic aldehydes only a few workers have studied the oxidation of these in sufficient detail to interpret their results in terms of a detailed mechanism of the reactions. Kinetic studies on the oxidation of formaldehyde by hydrogen peroxide, hydrogen peroxide in alkaline solution,? potassium permanganate, cobaltic ions,l ceric ions,j nitrogen dioxide,6 arid photochemical oxidations' have been made in some detail. 'IT3lliams and lVoodsx found t h a t aromatic and aliphatic aldehydes are oxidized by iodic acid. Studies on the oxidations of other aldehydes by hydrogen p e r ~ x i d e ,selenium ~ dioxide, l o potasi
1 1 ) J €1 Kastle a n d A . Loveilhart, THIS J ~ U R N A I . , 21, 2 0 2 ler. A i i i i . , 431,301 (1923). I89!)), 13. \Vieland a n d A . 1 ( 2 ) K \Virtz and ii. I' hoeffer, E . p h y s i f ? . C ' h ~ n z . ,B32, I00 C Qucllet, C ' i i i r . I . C h c n . , 29, 10-4ii ( 1 9 5 1 ) ; 1s A h e l . Z / > l i j s z k (.h
