The effect of temperature variations on the thermodynamic distribution behaviour in a silica C18/aqueous acetonitrile chromatographic system of polynuclear aromatic hydrocarbons is discussed. Evaluated enthalpy and calculated entropy change values are presented. The elution sequences of some polynuclear aromatic hydrocarbons are reversed by temperature variations, which ascribed to domination by entropy effects.

Very dilute solutions of clipl~ci~ylmcrcc~ry in carbon tetrachloritlc have been found not to have orientation polarization, but in not-so-tlilute carbon tetrachloriclc or in clioxane nncl benzene a t any concentration there is evidence of Inomeilt. Moreover, these moments vary ~legativcly in carbon tecrachloricle and cliosane ancl positively in benzene with respect to temperature. T h e angular C-I-Ig-C linkage responsible for orientation polarization is also clemonstratccl by appreciable moments for para methylmercuri-his-benzene ancl the hon~ol-ogous durene. hIagnitlrcles comparable with the aryl arlalog~ics are founcl for several alkyl his-n~erc~lrials, but the similarity in the moments of trifl~ioromethyl and methyl-his-mcrc~lry a s \\ell as a temperature coefficient for 11101ncnt of the latter compound indicates that the C-Ng-C linkage may vary wiclely ancl easily. I-Iowcvcr, a lower limit may be set by the moments of m e r c~~r a c y c l o h e s a~~c ancl merc~~racyclohcptanc in it-hich the mercury angle is lisecl by the cyclic structure.

No abstract

Furan and spll-an condensexvith aldehycles,chlorinatecl aldehydes and lietones, and keto acids, in the presence of hydrochloric acid. In niost cases, the corresponding difurylalkane or tlifuryl-substituted acid is formed. I n special cases the reaction stops a t the furylcarbiriol stage.Difurylallranes have been accessible, in the past, only through a variety of indirect approaches. Thus, for example, difurylmethane (V) has been prepared by Reichstein, Grussner, and Zscholtlte (7) by the reduction of difuryl 1;etone. Gilman and Wright ( 5 ) synthesized the same substance by the interaction of 2-cl~loron~ercurifura~~ and furfuryl chloride. Diilelli and Marini (3) treated ethyl furoate with trioxane in the presence of sulphuric acid. By subsequent saponification, h~.drolysis, and decarboxylation they obtained difurylmethane. This compouild has also been isolated as a product during the acid-catalyzed resinification of furfuryl alcohol (4, p. 222).Recently, Ackman, Brown, and Wright (1) have reported the formation of 2,2-difurylpropane by the condensation of furan with acetone in the presence of hydrochloric acid. Other methyl ltetoiles gave analogous products.In the present investigation, it has been found that furan also condenses with aldehydes, chlorinated aldehydes and ketones, and keto acids. T h e coildeilsatioll products are difurylalltanes in the case of aldehydes and ltetones. With lceto acicls, the corresponding difuryl-substituted acids result. Chloriilated aldehydes and ltetones, when condensed with furan, yield chlorinated difurylalliailes in some cases, while in others, unstable products, thought to be chlorinated furylcarbinols, are formed. Willard and Hamilton (8) have already reported the condensation of furan (I) with chloral (VIII) to form 1-furyl-2,2,2-trichloroethai~ol (IX).The investigation also includes the reaction of sylvan (2-methylfuran) (11) with the carbonyl compoullcls previously cited. Analogous prodt~cts are obtainecl. ';lla?izrscript received i n origi?ial fornt Decoilber 30, 1955, and, as revised, l l h y 25, 1966

!iBSl'1<.4C.l', .I hc ratio of isomeric bispcrchloratomcrc~~ribenze~~es obtairietl from the monomercurial ancl mercuric perchloratc in perchloric acicl varies slightly with concentration of the acid, but is prepondera~~tly meta. Howe\.er, more para than meta isomcr is o b t a i~~e d under conditions \\here the para isomer is insoluble ill thc s~~s t c~n .This indicates a mobile equilibri~~m among the isomers, which is found to estencl to all of the polymercuration p r o d~~c t s .The postulated intermediate for the equilibratio~~, which is 1,2,4-triclilorato~~iercuribenzene, is inclicated by the isolation of the similarly orie~~tecl 1,2,4,5-percliloratomercuritetral;ie1ze1ie. i\lthough nolle of the ortho-diperrhlorato~nerc~~ribe~~zene can be found fro111 this reaction in perchloric acicl, it is the principal isomer \\hen phenylmercuric acetate is acetos~~mercurated neat.