4867
TRITIUM LABELING REACTION OF ALCOHOLSAND ACETONE
Sept. 20, 1957 [CONTRIBUTION FROM THE
DEPARTMENTS OF CHEMISTRY,
PRINCETON UNIVERSITY AND UNIVERSITY OF KANSAS 1
Studies of the Tritium Labeling Reaction. 111. Alcohols and Acetonel BY WILFORD J. HOFF,JR., AND F. S. ROW LAND^ RECEIVED APRIL17, 1957 The reactions of tritium from the Li6(n,cu)Ha nuclear reaction have been studied in methyl alcohol, ethyl alcohol and acetone. All of the important non-gaseous products can be formed in a reaction involving the tritium atom and a single solvent molecule. I n these solvents, the most important reactions leading to non-gaseous products are ...; (1) T EC-H 4=C-T . , , ; (2) T EC-CH~ + EC-T
+
+
+
(3) T
+ -CH*OH
+ -CTO
+ . . . ; (4) T + >C=O
+
I
+ T-C-OH;
I
(5) T
+ =O+-OT,
T
+ -0-
-0T.
-+
tion times of 1 or 2 hours produced sufficient tritium activity Introduction to allow easy detection, without causing undue radiation Tritium atoms, recoiling with 2.7 MeV. energy damage in the solutions. The irradiations were carried out under a variety of exfrom the Lis(n,a)Hareaction and brought to rest in conditions. The most important of the varian organic medium, become incorporated into the perimental ables are listed in Tables I and 11, together with the results otherwise unchanged organic molecule in yields of of each experiment. All of the irradiations except experifrom 10-50% for a wide variety of organic com- ment 12 were carried out in the same water-cooled ,ocation pounds. Most of the organic compounds in which in the Brookhaven reactor; experiment 12 was carried out in the special liquid nitrogen-cooled facility. The nominal this reaction has been investigated have been SUE- neutron flux in the former was 1.8 X 10l2n/cm.2/st.c.; the ciently complex that isolation and identification of flux in the liquid nitrogen facility, 4.0 X n/cm.z/sec. Experiments 1 and 2 were carried out with ethyl alcohol all of the labeled species produced has not been attempted. I n most cases, investigation has been solutions sealed off, in the presence of air, in glass tubes with break-offs. These were cracked open in the restricted to the parent organic molecule itself, and equipped presence of additional ethyl alcohol carrier. Experiments to the distribution of activity within this mole- 10 and 13 were carried out with solutions sealed off in the absence of air. Prior to sealing, the acetone had been cule. The reactions of these “hot” tritium atoms have distilled back and forth several times in a U-tube, ,and the frozen solvent pumped on after each distillation. fifter irbeen investigated, however, in liquid methane and radiation, each sealed tube was cracked open while the conethane.4 I n these compounds, the primary la- tents were frozen down with liquid nitrogen, and then albeled tritium products are hydrogen and the parent lowed to warm and transferred to a stoppered bottle. Experiments 11 and 12 were carried out with solutions compound in roughly equal proportion, and totalwere irradiated in aluminum tubes approximately 5” ing 88 and 79% of the tritum activity, respectively. which long and I/,’’ in diameter. I n experiment 11, the tuties were The remainder of the radioactivity has been dis- packed in powdered Dry Ice throughout the irradiation tributed among non-parent hydrocarbons, both period. The rest of the irradiations were carried out in one tor more saturated and unsaturated, with molecular size up 15-1111. aluminum cups, equipped with tops in which a hole to Cd hydrocarbons, and larger. had been punched to prevent pressure build-up. Afi er irraThe SO+% yield of very simple products in the diation, the solutions were immediately transferred 1.0 stopmethane and ethane cases, together with the high pered glass bottles. Loss of solution during this type of yield of labeled parent compound in complex or- irradiation was negligible. The acetone solutions usually turned light yellow in color ganic systems, has led to the hypothesis that the during the irradiation, with the exception of experiment 9 final chemical combination for a n important frac- in which the dark blue D P P H solution tended toward a tion of the tritium occurs a t rather low energies, reddish-brown color after irradiation. The yellow color and involves only the tritium atom and one dis- was very much lighter in experiments 8 (20% water by weight) and 12 (solid). The alcoholic solutions all were rupted molecule.3b colorless following irradiation. I n order t o verify or supplement this hypothesis, Derivatives.-After each irradiation, appropriate carwe have extended the investigation of these tritium riers were added to the irradiated solution, usually in sepaatom reactions t o further simple molecules: rate experiments for each carrier. The carriers were often from the parent compound by vacuum tiistillamethyl alcohol, ethyl alcohol and acetone. We separated tion, followed by the precipitation of a characteri5,tic dehave attempted t o account chemically for all of the rivative. In some cases, the derivative was precipitated non-gaseous tritium produced in neutron irradia- directly from the solution of both carrier and sample. These derivatives were then recrystallized first to the correct tions of solutions of lithium salts in these solvents.
melting point, and then to constant specific radios ctivity through several successive crystallizations. The particular derivatives used were chosen because very little exchmge of labile hydrogen took place during their Formation, as well as Irradiation.-All of the irradiations were carried out on for their relative ease of formation. Most form readily a t liquid solutions of either Lih’Oa or LiCl, with the exception room temperature or require only slight heating. of one run on a solid solution of LiN03 in acetone. IrradiaThe derivatives were prepared as follows. 1. Alcohols.-The alcohols were first distilled From a (1) Research supported in part by A.E.C. Contract No. AT(11-1)solution of I-ml. sample, 1 ml. of the appropriate alcohol as 407. carrier, and 25-500 ml. of water, collecting approximately 1 (2) University of Kansas, Lawrence, Kansas. ml. in the appropriate temperature range. This distillate (3) (a) R . Wolfgang, F. S. Rowland and C. N. Turton. Science, 121, 715 (1955); (b) F. S. Rowland, C .N. Turton and R. Wolfgang, THIS was added to 3,5-dinitrobenzoyl chloride; the precipitate of 3,5-dinitrobenzoate was washed with 2% NazCOa solution JOURNAL, 78, 2354 (1956); ( c ) F. S. Rowland and R . Wolfgang, and water, and recrystallized from ethanol-water and/or Nucleonics, 14, No. 8, 58 (1956). methanol-water solution. (4) R . Wolfgang, J. Eigner and F. S. Rowland, J. Phys. Chem., 60, 1137 (1956). Isopropyl alcohol was isolated from the ethyl alcohol
Experimental
4568
WILFORDJ. HOFF,JR,,
AND
F. S. ROWLAND
TABLE I Ethyl alcohol
VOl. 79 -.
Methyl alcohol
Irradiation no. Wt. organic, g. Wt. Li salt; g. Irradiation conditions
1 2 3 14 4 1.34 1 .o 19.2 19.8 19.2 0.20 LiCI 0.16LiCl 0,GO LiNOa 0.60LiiYO, 0.61LiNOJ 1 hr. in sealed 6 hr. in sealed 1 hr. in ventcd 2 hr. in veiited 1 hr. in vented tube tubc A I cup A I cup :I1 cup C-Tactivityinparent coxnpd. dpin./ing. 2600 & 150" 20400 f 300" 3120 f 50 5100 f 100 3110 i 70 c c Calcd. total activity produced 13,500 26,300 13,700 c c 70 Total T as C-T in parent 23 20 23 Activity rela.tive t o C-T in parerit e HzO exchangeable 0.90f U.10 0.85 f 0.05 1.24f 0 . 0 4 c Methyl alcohol 0.06 f 0.01 0.08 A 0.01 0.06 A 0.01 Ethyl alcohol 0 .01 c c i-Propyl alcoholb 50.02 0.02 0.02 c c c Ethylene glycol 0.01 0.01 c c 0.05 f 0.01 Formaldehyde 0.01 Acetaldehyde 0.06 f 0.01 0.05 =k 0.01 0.09 f 0.01 0 . 1 2 f 0.01 c c C B.p. >looo 0.01 Total non-gaseous 1.86 f 0.10 1.91 A 0.04 1.88f 0.05 1.88 f 0.05 2.25 f 0 . 0 3 Some loss of solution in adding t u carrier; heuce, specific activity of original unknown. Primary Iiydrogens only. Kot measured. solutions by oxidation t o acetone with KMnOa and MgSOa, Results followed by formation of the 2,4-dinitrophenylhydra~one.~ The experimental results for the irradiated soluThis, of course, gives only the tritium activity present in the tions in alcohols are given in Table I ; for acetone, primary hydrogens of isopropyl alcohol. 2 . Aldehydes .-Formaldehyde and acetaldehyde de- in Table 11. The results have been expressed for rivatives were formed from both ethyl alcohol and acetone the parent molecule in terms of the observed specific by addition of 3-ml. sample, 1 ml. of aldehyde carrier, sodium acetate, and HC1 in ethanol-water solution, to a large excess activity and the percentage this represents of the calculated total tritium production. The yields of dimedone solution. The aldehyde-dimedone precipitate was recrystallized from ethanol-water solution. of other products have been expressed relative to Acetaldehyde also was isolated in experiments 1 and 2 as that of the parent molecule, rather than in perthe semicarbazide and in experiment 3 as the 2,4-dinitrocentages of calculated total activity, in order to phenylhydrazone. 3 . Acetone.-Acetone was always isolated as the 2,4- eliminate uncertainties in actual neutron flux for dinitrophenylhydrazone by addition of 1-ml. sample t o 100 each irradiation. Any variation in this relative d. of a saturated solution of 2,4-dinitrophenylhydrazine ratio could then, of course, be caused by variations in 2 N HCI, and recrystallization from ethanol. in yield of either the labeled parent or non-parent 4. Ethylene Glycol.-Three ml. of sample was added to 1 ml. of ethylene glycol carrier and 10 ml. of pyridine. molecule. After vacuum distillation of this solution to remove the alConiparison of the total non-gaseous activity cohol and part of the pyridine, benzoyl chloride was added, with the sum of that found in each chemical species the solution heated, and the dibenzoate precipitated by indicates, within the errors, that the major nondilution with water. The precipitate was recrystallized gaseous tritium products have been identified. from ethanol-water. 5 . Ethanol-to-acetate.-Ethyl alcohol was oxidized to Experiment 9 is an exception in which a large fracacetic acid with potassium dichromate in sulfuric acid. tion of the activity carried with the DPPH residue The acetic acid was distilled from the solution, neutralized with XaOH and evaporated to dryness. The sodium acetate and was not exchangeable readily with water. Table 111 shows the intramolecular distribution was recrystallized from ethanol. A portion of the sodium acetate was dissolved in acidic ethanol and precipitated with of the tritium in two cases. Table IV summarizes p-bromophenacyl bromide. The p-bromophenacyl acetate the pertinent data on exchange reactions involved was recrystallized from water. 6. Acetaldehyde-to-acetate.--Acetaldehytle was oxi- in derivative preparation, and lists the observed data from experiment 3 for comparison. dized t o acetic acid by (a) Benedict solution or (b) potassium dichromate, and the resulting solution treated as above to Discussion produce sodium acetate and p-bromophenacyl acetate. There are two obvious paths by which tritium acLabile and High Boiling Tritium.-Several nil. of water was often added to a few ml. of the sample, and thc solutivity can be introduced into these compounds tion fractionally distilled. The amount of labile tritium other than by direct reaction of an energetic atom present was measured through the radioactivity of the nextto-last cut from this distillation. The excess tritium ac- or ion with the parent molecule. The first of these tivity of the final cut (residue of undistilled liquid) over that is by exchange reactions with labile tritium present of the pure water fraction was the measure of the activity in the system. Such exchange might take place bound in compounds with a boiling point greater than 100'. either with the carrier material after i t is added, or In thrise cases in which two water cuts other than the residue with the carrier or precipitating agent during de[vcre measured, the agreement in specific activity u-LLS very rivative formation. All such exchange reactions satisfactory. Counting.-The tritium activity was measured by &is have been shown to be slow under our conditions proportional counting of the mixture of gases produced b y by t h e experiments listed in Table IV. The extent treatment of the sample with zinc, nickelic oxide, and w:ttcr of these exchange reactions is sufficiently sinall a t 700O.6 The normal counter filling consisted of 34 C I U . that they can be considered negligible except for ethane plus the active gas (-1 cm.). ( 3 ) L. Kaplan, THISJ O U R N A L , 77, Z l C i O (1955). (ij) E;. Wilzbach, L. Kaplan and 1 %'. G. Brown, S ~ t e i i ~ e118, , 522 (lYX?).
those constituents which appear to contain 0.5% or less of the total tritium produced by the nuclear reactions.
TRITIUM LABELING REACTION OF ALCOHOLS AND ACETONE
Sept. 20, 1957
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