The Synthesis of Carbon-Isotopic' Alkanes: Methane-C13, Propane-l-C13, n-Butane-l-C13, n - B ~ t a n e - l - C ~I~obutane-l-C'~, ~, Isobutane-lC14 and Isobutane-2-CT1
e. 1 )
7. \\ O T \ O S Studies undertaken 111 tliese laboratories 011 the mechanisms of certain hydrocarbon reaction^^^^^ have necessitated the syntheses of certain isotopic hydrocarbons containing either deuterium, C L 3or C14. Syntheses of the monodeuteroalkanes have been treated separately6; this note concerns the syntheses of the several carbon-isotopic alkane\ used in these investigations. All of the compounds, with the exception of 71b11tane-l-C~~ and isobutane-2-Ci3, were prepared on a 5-20 millimole scale. The reaction schemes There were no non-isotopic impurities in any of are as follows, with the over-all yields indicated7. the products (limit of detection inass spectrometrically is approximately 0.1%) except %-butane?"lg 1 -CX4,which contained small amounts of n-hexane ( a ) Cf3'11,1 Cl3IIi (86r; virlrt) IT and propane. Snalyses of the propane-C13and butanes-C13 for the isotopic speciesp and isotopic isomers were made by direct mass spectrometric examination. The data are reproduced in Table I . The methane-Cla isotopic composition was found to be 50.0 * 0.3 atom 7*C13 by burning a sample completely to carbon dioxide and analyzing the latter tilass spectrometrically. The isotopic concentrations of the three radioxctive alkane preparations, as determined by use o f an ionization chamber, were : n - b ~ t a n e - l - c ' ~ , 0.062 nit. /millimole; i s ~ b u t a n e - l - C0.0026 ~ ~ , and 0.077 tnc. millimole. BY
i\'ACWf
R, 1 ) . 1'
SI
('N A i l )
$p5
TABLE
1
IC1(7TOPIC COMPOSTTIOX3 OF
Propane1.CIY
( 1 ) The systein of nonienclattire uwd (J. W. Olvos and C I>. Ii'aguer, Scit?icr, 106, 409 (1948)) is an extension of that alrrady adopted 11y the American Chemical Society for deuteriii 111 win-.
irounds. (Jccasional obvious departures from the system (c.g., isolmtane-l-C1s instead of the more proper Z-methylpropane-l-C'3) have been made for purposes of clarity. (3) 0. Reeck, J. W. Otvos, D. P Stevenson and C. D. Wagner, .I. C'irem. P h y s . , 16, 255 (1948); 17,418 (1949). (3) J. \V. Otvos, D. P. Stevenson, C. D. V'agner aitd ir. I k e r k , ibid., 16, 7-15 (1948). ( 4 ) D. P. Stevenson, C. D. Wagner, 0. Reeck ~rl>il J. \I'O t v o s . ibid. 16, 993 (1948). ( 5 ) C 1). Wsyncr, 0. Rerck, j. TT'. 0tvo.i and D I' Stevenson, ihd,17, 419 (19.491. (6) C. 1). IT'agner and D, P. Stevenson, T i u s J < ) I . K u I . . 72, 57% (1 950) . (7) For complete experimental details of tlirse syntheses order Ilocurnrnt 3028 from Arnerican Documentation Institute, 1719 X. Street. S . W., Wahsington 6, D. C., remitting $0.50for rnicrofilni (images 1 inch high on standard 35 mm. motion picture film) or $2.10 for photocopies (6 X 8 inches) readable without optical aid. is! Methyl-ClZ iodidr way not available a t the time this pair of isotopic compounds mas synthesized. Procedures based upon it as starting material, siicli its t c ) , would h a v e been superior to the procedures w e d .
i \ l k : i t i e C ~ ' ~ 4:.7 * 0 . 5 Alb:iiir CI" 5 3 2 3: 0 . 5 . A l k a 1 i e . l - C ~ 15~2 . 7 -+ 0 . 5 jiIkaiir-2 CI" 0.53 * . 0 . 0 1 , & l k a n e - C i ~ ~1 I 2 -1 0 0 2 ( ! I 3 rOllteItt oi t l i c Cl3 re agent' used in synthesis
THE
ALKANES
Mole % n-ButaneIsobutanei-ci3
I-c13
81.0 1 0 . 3 50.3 h O . 5 18.4 * 0.2 48.2 t 0 . 5 1 6 . 8 * 0 . 2 47.7 * 0 . 5 1 . 6 4 * 0 . 0 2 0.51 *0.01 0 12 * 1) 02 1.44 f 0 . 0 2
53.3
16.5
48.2
Isobutane2-Cij 8 1 . 5 * O :I 18.0* 0 2 2.47 3. 0 02 15.5 + O 2
0 49
.%-
I1
02
16.0
Cdculateci from the isotopic species distribution in this table, Values determined should be equal to the C13 content of the CIS starting materials if there is no isotopic dilution in the course of the synthesis. '1
SHELL L~EVELOPMENT Co. I?MEKYVILLE, CALIF.
RECEIVED OCTORRR 21, 1950
(9) I n this and relsted reports from this laboratory, the term "isotopic species" and "isotopic isomer" are defined in the following way: Molecules of il given "isotopic species" of a chemical compound all contain the same number of isotopic atoms of a given element. "Isotopic isomers" of the same isotopic species differ only in the positions of the isotopic atoms in the molecules. For example. propane-1,3-C:' and propane-l,2-Cis a r e isotopic isomers of the isornpic Eperies j r r t , , x x t i r - ~ " .
