A Convenient Synthesis of DCI and HCI-sCI A recent article in this Journal ( I ) described a procedure for the synthesis of DCI by the reaction between DzSOl and excess KCI. It happens that we described the synthesis of DCI by a closely related reaction (NaCI was used instead of KC11 almost 20 years ago (2),hut that is not the point of this report. Rather, we would like to direct attention to the advantages inherent in the use of the so-called "Brownz hvdroeenator" for such reactions. As Brown has ~ o i n t e dout (31, this device. w h ~ uar h ori~insllydesigned fur thr catdyrif hydkgenation of alkenes (4,, can be usrd for ;he rapid, quantitative, and a u t ~ ~ m a t i c s y n t h e a i s opf m a ~r h o f ran h o g e n e m f e d b) t h e r e a c l i v n hetu.ern tu n ltqutdeora l ~ q u i d o n d as o l d I t isespel since the reaction rialls suited fur applications whwe it is deimed that the gas undergo a subsequent r h ~ m i r a reaction, occurs in the same apparatus in which the gas is generated. (1) in the We carried out the deuteriaehlorination of 2-chloronorhorene to 3-ero-deuterio-2,2-dicMoronorbornene Brown2hydrogenator by replacing the inlet valve with aglass syringe connected to the apparatus withaTeflonneedle, thus avoiding contact hetween D2S01 and metal parts (2). Addition of DCI to the alkene occurred rapidly and quantitatively when the center reaction flask of the apparatus containing the alkene was cooled to -78 'C (5).
Our interest in 2-ero-"C1-2,2-d~chlo10no~horn~ne (2) called for a somewhat different experimental configuration (6). "C1 is most commonly available in the form of labelled constant-boiling hydrochloric acid. However, hydrogen chloride gas is not evolved when constant-boiling hydrochloric acid is added to concentrated sulfuric acid; the two liquids mix without gas evolution because of the high water concentration in the hydrochloric acid solution. We found, however, that the constant-boiling, labelled hydrochloric acid solution could be mixed with unlabelled concentrated hydrochloric acid (1 part of constant-boiling to 15 parts of concentrated acid) to produce a solution that will evolve hydrogen chloride upon mixing with sulfuric acid without unduly reducing the specific activity of the resulting H"C1. In this case, it was more convenient to place the more corrosive sulfuric acid in the reaction chamber of the Brown2 apparatus, and to add the hydrochloric acid solution to it. Substitution of deuteriosulfuric acid would permit synthesis of the doubly labelled W DCI (7).
Albert J. Fry Weslayan University MiddMown, CT 06457
366
Journal of Chemical Education
