bered series, which is characteristic of long-chain compounds ( 2 ) . The average increase for each additional carbon atom is approximately 1.12 A. for the dithiol esters of sebacic acid. This is less than the accepted value of 1.27 A. for the projected carbon-to-carbon distance. It appears that the dithiol esters of sebacic acid crystallize .in tilted monomolecular layers, as do the diethyl esters of dicarboxylic acids, containing an even number of carbon atoms in the chain ( I ) , and n-aliphatic thiol derivatives of monocarboxylic acids ( 5 ) . The values of the long spacings reported ( 1 ) for the diethyl esters of dicarboxylic acids, containing an even number of carbon atoms in the acid chain, are approximately 0.2 A. larger than those of the corresponding dithiol esters given in Table 11. This indicates that in both series the compounds crystallize with approximately the same angle of tilt. The dithiol esters containing an even number of carbon atoms in the thiolester groups have long spacings which are slightly greater than those containing an odd number of carbon atoms in the thiol ester group. This is the same as was reported for thiol esters of monocarboxylic acids ( 6 ) . I n general the rererse is true for long-chain aliphatic compounds containing odd and even numbers of carbon atoms in the aliphatic chain ( 2 ) . SUMMARY
X-ray diffraction powder data were obtained for 9 n-alkyl dithiol esters of sebacic acid. All individual compounds can be readily identified and distinguished by the x-ray diffraction data.
45
r--I I
-
40L
s:
30t
a"
I
// //
I
2
0
4
CARBON ATOMS
Figure 1.
0
0
1i
/ / O
/'0 .e /
35
m
/ I
/
I
L
m
I
8 IO ESTER ALKYL
6
IN
12 GROUPS
Long spacings of dithiol esters of sebacic acid
Even number of carbon atoms in each alkyl group in ester Odd number of carbon atoms in each alkyl group in ester
The long spacings increase regularly with increasing ester-chain length forniing an odd and an even series. The n-dialkyl dithiol sebacates crystallize in niononiolecular tilted layers. LITERATURE CITED
(1) Francis, F., Collins, F. J. E . , Piper, S. H., Proc. Roy. SOC.(London) A158, 691 (1937). (2) hlalkin, T., h'ature 127, 126 (1931).
(3) Sasin, R., Weiss, G. S., Wilfond, -4. E., Sasin, G. S., J . Org. Chem. 21, 1304 (1956).
(4)Urquhart, G. G., Gates, J. W., Jr., Connor, R., "Organic Syntheses," Vol. 21, pp. 36-8, New York, Wilev. 1941. ( 5 ) \Titmi&, 1,. P., Lutz, D. A , , Sasin, G. S., Sasin, R., J . Am. Oil Chemists' SOC.34, 71 (1957). RECEIVED for review May 14, 1957. .4ccepted July 16, 1957. Submitted by D: A . Lutz in partial fulfillment of the requirements for the master of science degree at Drexel Institute of Technology. Mention of company or trade names in this paper does not imply endorsement by the U. S. Department of -4griculture over similar concerns or products not mentioned.
Mass Spectrometric Analysis Aliphatic Ethers FRED W. McLAFFERTYl Spectroscopy laboratory, The Dow Chemical Co., Midland, Mich.
b Correlation of the spectra of 25 saturated aliphatic ethers shows the unique usefulness of the mass spectrometer in identification, structure determination, and analysis of such compounds. These mass spectra show marked similarity to the spectra of other compounds with electron-donating functional groups, such as alcohols and amines. Cleavage of the bond alpha to the oxygen atom i s favored to yield the alkyl ion, especially in symmetrical and nonbranched ethers. Beta bond cleavage to give the oxygen-containing ion i s prominent, especially in methyl ethers. Alpha branch1782
8
ANALYTICAL CHEMISTRY
ing favors the cleavage of a beta and opposite alpha bond with rearrangement of a hydrogen atom. Anomalous ions found at one mass unit above the molecular weight are formed by intermolecular recombination. These can b e found with many other types of compounds other than ethers and can be useful in molecular weight determination. Mechanisms for these favored cleavages are proposed.
P
correlations of the mass spectra of saturated aliphatic amines (4-6, 16) and alcohols (9, 18) have shon-n marked similarities, such as the
strong tendency for cleavage a t the beta carbon-carbon bond
R'
It '
R"
R"
to give the positive ion containing the functional group. It has been suggested (17, 18) that these spectral wnilarities are caused bj7 the siniilar
REVIOUB
1 Present address, Eastern Research Laboratory, The DOTT Chemical Co., Framingham, Mass.
electron-donating powers of the hydroxyl and amino groups. The present study of saturated aliphatic ethers was undertaken to see if the ether group caused similar bond cleavages, and if it caused rearrangement peaks (ions that cannot arise from simple bond cleavages) similar to those found in secondary and tertiary amines ( 1 4 ) . EXPERIMENTAL
The spectra of 25 saturated aliphatic ethrrs were obtained. Most were run on two 90" sector-type instruments ( 3 ) v i t h inlet systems heated to 100" and 200" C., respectively. Spectra taken from the A P I catalog of spectra ( 1 ) vere run on Consolidated Engineering Corp. Model 21-103 mass spectromcters. The spectra from the latter type instrunient were qimilar a t higher niasscs to those from the 90" machines of this laboratory, though the small ions-e.g., CHB+-tended to be markedly more aliundant in the CEC spectra. Percentage figures n ithin parentheses given in the text refer to the relative aliundance of the particular ion compared to the most abundant ion in thc SpeCt 1'11111. RESULTS
The spectra examined are shown in Tnlile I. Though the molecular ion decreasrs rapidly with increasing nioleculnr weight, it remains significant (37,) t,lirough Clo ethers, and apprecialile enough for use (0.1%) through (316. C1i:iin branching usually decreases the significance of the parent peak, and it is nf little use for the tertiary cthers. Alpha cleavage is important, especially in t h e symmetrical ethers, t o give the alkyl ion.
R-
1
-0-R'+Rf
f OR'
Table I1 s h o w the relative abundance of the alkyl ion, R+, from the molccule ROR'. These abundances are not corrected for contributions from fragments of the same mass arising from other modes of breakdown. Peaks iinderlined are the largest of any ions of the gcneral formula C,,H2,+1in the particular spectrum. This cleavage gives the largest peak in the spectrum for di-n-propyl through the di-n-hexyl cthers, and this peak is still very proininent (13749 in the di-n-decyl ether. The peak one mass unit belon is even slightly larger in both these higher molecular IT-eight ethers and in some with branching somen-hat removed from the oxygen-e.g., diisoamyl ether. This can be thought of
as loss of R O H in the same m-ay a significant peak is formed in alcohols
R'OCH?CHZR++ R'OH
+ CH*=CHR+
by loss of WOH (9, 18). I n the mixed ethers, branching on the alpha carbon appears to favor the abundance of that alkyl ion formed. A t alkyl groups of the iise of n-octyl and isoamyl, and larger, the typical lower alkyl fragments of the paraffins predominate, especially m/e 43 and 57, and to a lesser extent, m ' e 71, etc, The alkyl ion of one less CH2 than that from alpha cleavage (the ion from beta cleavage in non-alphabranched ethers) is small. If one of the alkyl groups is methyl, neither alkyl group is as clearly indicated by the relative sizes of the various CnH2n--l peaks. is used to refer t o peaks of the series m 'e 15, 29, 43, 57, etc., recognizing that ions as CnHzn-10 can also contribute here.) With all straight-chain ethers below CI6 and branched ethers below Clo, other than methyl, that n-ere studied, the largest C,HZnT1peak n-as the same inaqs as one of the alkyl groups of the ether. The other ion possible from alpha cleavage, OR'+, is generally not as important, though some ethers-e.g., diethyl, ethyl n-butyl-give appreciable peaks b y this mechanism. H o w v c r , it does not appear to he significant n i t h ethers above C6. Beta cleavage, as noted for amines a n d alcohols, is favored t o give t h e oxygen-containing ion.
When the bonds are equivalent in this way, the one giving the loss of the largest alkyl group is favored. Thus, n-propyl n-butyl ether gives a mle 87 (loss of 29) peak of 13y0relative intensity, and mle 7 3 (loss of 43) peak of 24% relative intensity. At masses above that from the loss of the largest alkyl group by beta bond rupturee.g., above m,le 73 in n-propyl n-butyl ether-the loss of the second largest such alkyl group usually gives the CnH2n--10peak of highest intensity. The n- and isobutyl ethers give the exceptions in the spectra studied. CleaTrage of the beta bond to give the alkyl ion appears to be of no significance. Alkyl ions from both alpha and gamrna bond scission apparently are highly favored over beta. REARRANGEMENT IONS
Alpha and beta cleavage with hydrogen rearrangement t o t h e oxygen-containing fragment can explain prominent peaks in a number of ether spectra (Table IV).
R
I I + C-OH+ + C=CI I 1
This type of cleavage is not noted with inethyl ethers, indicating that a beta hydrogen is necessary for the rearrangement on cleavage of the alpha bond, This same multiple cleavage with rearrangement has been noted for the analogous secondary amines
(14).
Table I11 shows the relative abun-
I
dance of the ether ion C-OR'+, thus I formed. Ethers less favored for the alpha cleavage give prominent beta cleavage. Thus, with methyl ethers, the ether ion containing the inethyl u-as the largest peak in erery spectruni examined, For example, every methyl ether with no alpha side chain gives 172 'e 45 as the largest peak in its spectrum. (Every ether with m / e 45 as the largest peak is not necessarily a methyl ether, however.) For the ethers studied u p to clidccyl n ith no alpha substitution, this beta cleavage yields the largest peak in the C,H2,+10 series. Diethyl ether is an exception, but the other two non-alphabranched ethyl ethers give thcse as the largest peaks of t h e spectrum. The relative abundances of ions of this type decrease with increasing molecular size. I n mived ethers, cleavage of the beta bond to a tertiary carbon is favored over that to a secondarv carbon, ctc.
K h e n neither alkyl group of the ether molecule is methyl, this rearrangement is especially prominent where a n alkyl group is alpha substituted. Thus all tert-butyl ethers studied yield large (>43%) m/e 59 peaks, and all iso-propyl or sec-butyl ethers yield large (100% in present examples) 45 peaks. These were the largest peaks of the formula CnH2ni10 for all compounds studied. For ethyl ethers, the mass 31 ion is prominent (>60%), but for larger alkyl groups with no alpha branching the 7n:e 31 peak is not especially significant (1 to 77,). Though beta cleavage also yields abundant ions of the formula C,Hz,+LO, it occurs most proniinently with ethers containing no alpha branching, in contrast to this rearrangement mode of degradation. The largest peak in the spectrum of dicyclohexyl ether is at mass 100. Alpha and beta cleavage with hydrogen rearrangement would give this ion, as a single beta scission would cause no loss from a ring entity. T h e rearrangement loss of H 2 0 appears t o be involved in significant VOL. 29, NO. 12, DECEMBER 1957
1783
Table I.
m/e 15 27 28 29 30 31 32 33 41 42 43 44
45
Meth Eth
lleth nProp
Meth
Dinieth
Isoprop
Dieth
11
(11
Ii
(1)
D
46
ti0
0.2 0.9 39 1 3 0.1
20 8
..
0.1
0.3 1 0.6 100’
49c
3 20
57 58 59 69 70
3d 6
2 8 0.3 2
74
25d 18 4 33
2 18
0.8
0.2 0.8 8
2
2
I
4c
29
e
0: 1 0.1
, .
..
158
.. 0.1 11 1
0.1' , .
0.4 0 .4 0.2 0 . :3
0'3 0.6
0.1 0.1
. . . .
0.1 0 1 1). 1
0: 1
..
1
18 16 33 1 ie 0 7 63 26 100 14 ti i 3 tj4
0 1
07 0 9 1 0 7 0 0 0 4 1'
(Continued on next p a g e )
VOL. 29,
NO. 12, DECEMBER 1957
1785
. Dimeth
Meth n-
Meth Eth
~-
Meth Isoprop
Prop
Table 1.
Compound Meth Meth nIsoBut but
Dieth
Mass Spectra of Aliphatic
Meth secBut
Meth tertBut
Eth Isoprop
Eth n-
But
Eth IsoBut
(1)
S
(1)
C
(1)
Source* (11
h1
K
46
60
74
61
26
18
D
(1)
I< (1) Molecular Weight 88 85
88
74
71
7
36
2
6
1
1.91
0.90
1.46
2.32
1.78
88
102
88
102
182 183
184 185 196 197 198 199 210 211 224 238
Molw. ion
0.85
S~/Sip,lf,h
1.72
1.51
1.08
2
4
7
2.26
0.96
1.35
a B, Brothers. C, Carbide & Carbon. D, Dow Chemical. E, Eastman Kodak. K, K & K Laboratories. hl, Matheson. S, Shell Development.
Ether ion, beta cleavage loss of next larger group.
(though relatively small) peaks of t h e C,H9, series found in the large ethers,
the spectra of aliphatic alcohols (10, 18). Acetals are a special type of diether of t h e general formula R’-0CHR-0-R’. Friedel and Sharkey have found (9) that preferred acetal fragmentations involve rupture of (A) a C-0 bond with loss of -OR’ and (B) the C-R bond with loss of R. These are typical ether cleavages found in this work of (A) alpha cleavage to give the “alkyl” ion and (B) beta
di-n-octyl and higher. Thus above ?n’e 211 di-n-decyl ether (molecular weight 298) has its highest peaks a t masses 224 (0.3%), 238 (0.2%), 266 (0.8%), and 280 (0.8%). Loss of water and none to three CH, groups with recombination of the large alkyl groups could give such ions. Loss of 18 mass unitsis oftenaprominent peak in _
_
_
~
~
~
cleavage to give the oxygen-containing ion, Mechanism A will also explain the base peaks of di-n-propoxymethane and di-n-butoxyethane, as well as large ions of other acetals. The third major degradation mechanism of ethers postulated in this paper can account for other major peaks in the spectra of the acetals. Thus from Table IT’ any acetal with R’>CHs and R==CHS (acetals of acetaldehyde and ethanol
~
Table II. Alpha Bond Cleavage, Aliphatic Ethers
1
R 0-R’ R’,
Wher? -OR Lost Meth Eth
Ion, R +
~~~
C1 C?
n-C1 i-Ca n-C4
i-C4 S-CI t-C,
24a 25 3 25 2 15
49 41h -
16 2
34 -
..
17 25 -
43 20
nProp 4 ..
Iso-
n-
prop
But
29 32 -
23
100 .. -~ .. 39 E0 . . . .
. . .. . .
Isohut
2
2 13
85
..
..
..
.. .. ..
100c __
..
..
..
l0OC
nHex
n,-
2-
Oct
EtCa
nDec
25
..
..
, .
Isoam
-_36
100 -
. . ..
..
.. 100 __
90
100 -
16
3
13
See footnoteb in Table I. Peak underlined is largest, C,HW peak in spectrum. Similar cleavage at other R groups will give same m / e .
1786
10
..
2-I’tCe n-Clo a
nAm
.. ..
n-Cs
c
tert-
But
..
~
n-Cj i-C, n-C,
S-
But 5
ANALYTICAL CHEMISTRY
Ethers (Confinued from page 7785)
Eth
Dinprop
Eth tertBut
sec-
But
Diisoprop
n-
Di-
Propn-but
n-
Compound Isobut tertbut
but
~
Di-
Dinam
Dinhex
190-
am
Bis(2-eth Hex)
Uinoct
Uin-
dec
Molecular Weight 10%
102
10%
102
116
130
158
130
15s
186
24%
0.1 0.1
.. .. . .
..
.. 1.47
6 0.83
2 1.26
3 1.17
or higher alcohols) should give a significant mass 45 ion by alpha and beta cleavage n-ith hydrogen rearrangement.
CH,
CH3
R’O .
+ -AH-OHT.
+ CH,=CIJR”
2 2.16
0.1
0. 1 0.2 0.3 0.2
..
..
0.1 0.46
0.54
0.8 0.8 0.0 0.13
..
c1
C,
cZ
n-C3
loon -
11’ 53
2
..
28
15 ..
100 100
C? n-C3 i-C3
100
100 100 100 13 100 -
..
100 100 - 51
n-C4
i-C4 s-c4
~
s-c4
4c 38
24
.. .. .. ..
0.1 0.86
..
..
and, in the latter compound, from
tion of the nonrearranged ion -OC2Hc can also contribute to m/e 45 in diethoxyethane.) Similarly the largest peaks in diethoxymethane and diethoxypropane can arise from this rearrangement
For most of the ethers studied a peak has been noted a t one mass unit above the molecular n-eight (U 1). The relative abundance of this peak increases with increased sample pressure and with
-OC3H7. ANOMALOUS IONS
+
Beta Bond Cleavage, Aliphatic Ethers
R-
I I
0.2 0.62
3 0.40
..
This is the largest peak in the spectra of diethosyethane and di-n-propoxyethane, and second largest in di-nbutoxyethane. (The less likely forma-
Table Ill.
R-C-
.. 1.17
..
0.2 0.2 0.1 0.4
..
1 1.61
0.2 0.3
..
i-C3 4
n-C4
..
0.7 2 13
24
.
28“
.. .. .. , .
.
19 -
.. .. .. ..
.. f-C4 n-C5 i-C5 n-Cs n-Cs 2-EtCe n-Cio a Peak underlined is largest CnHTn+ peak in spectrum. See footnote Table 11. See footnote b , Table I.
II
-C-0-R’ Ion, C-OR’+, I I i-Ca s-C4 0.8 1 0.3
4c
. ..
..
.
.. .. .. ..
15
.. .. .. ..
..
..
Where R’Is t-C4 0.1 38
43%b)
Largest
(R
=
Are, E t )
m/e 45 ( 1 0 0 ~ o )
Largest
I
C C R-C-0-C-CH
(R = AIe)
R-C-O-C-CH
Majora
m/e 31 (>GO%)
I
H Not significanta
R>Me m/e 31 (1-7%) C,H2,+10 peaks from beta cleavage are still important. Relative abundances of particular peak in spectra studied.
the decreased ion dran out (repeller) potential. Thus in Table V the relative abundance of m ’ e 89 for tert-butyl methyl ether, molecular iveight 88, increases by a factor of 9, by far the largest variation found in any of the peaks froin mass 12 to 110. Further investigations of this laboratory have shonn that the M 1 peak is a general phenomenon in the mass spectra of a number of compound classes-e.g., alcohols, ethers, amines, glycols, and nitriles. Because most compounds of higher molecular weight in these classes give insignificant molecular ions, the N 1 peak can be very useful to indicate the molecular weight. If the spectrum of the unknon-n is rescanned through the higher mass range a t reduced ion drawout before the sample is pumped out, the M 1 peak should be obvious by comparison of the t n o 5cans. Anomalous ions of this nature were first noted by TT’ertzler and Kinder (23) in the spectra of 11- and isobutyronitrile. They demonstrated that the relative abundance of this d l 1 peak was proportional t o the square of the sample pressure, indicating formation by intermolecular reaction. LOVering
+
+
+
+
Table V.
a 5
Anomalous Ion of Mass Ion
the ion drawout potential increases the residence time of the ions in the ion source raising the probability of this reaction. Later work (19-21) has shom-n similar M 1 ions arising from reactions such as the following:
+
+ H20 CH4+ + CH4 8 + + Hz CHIOH + CHSOH H20T
+ HO CHj+ + CHJ AH+ + H CHjOH2 + CHI0
+
H30+
+
+
+
+
ANALYTICAL CHEMISTRY
+
This mechanism would account similarly for the A l 1 ions found in this work. Methanol (19) has a relatively high specific reaction rate. As has been observed for Tvater (21) and the butyronitriles (WS), increasing the sample pressure of the ether, etc., by adding another organic compound in a broad range of types ill also increase the relative amount of the AI 1 peak. I n using the ill 1 ion to determine molecular \\-eight, it should be noted that ions other than a t m/e X 1 have been found, showing variation of related abundance with sample pressure and ion dran-out. Beynon has stated ( 2 ) that for nitriles he has ob-
+
The use of these generalizations for structure determination provides information not available from other techniques. The partial spectrum in Table V I illustrates the use of the method. The effect of sample pressure and ion drawout voltage on m / e 131 point to 1 peak, indicating a this as the Af molecular weight of 130. One mechanism of molecular breakdown discussed gives significant peaks in the CnHZn+l series of ions, and the other t n o in the C,H2,+10 series. Thus the base peak a t 57 strongly indicates a butyl ether (alpha cleavage mechanism). With a molecular Iveight of 130, this then would be a dibutyl ether. The large 59 ion (CnH2n+10)can arise, if by a beta cleavage mechanism, from C2H5--O= m’e 59) or CH2-R (C2-0-CCH3.O-CH(CH3)-R (C-O-CZ= m/e 59); or, if by an alpha and beta cleavage with hydrogen rearrangement, from R-C(CK&-O-R’ or R-CH(-C3-0= m/e 59). (C?Hs)-O--R’ The first two are not butyl ethers, and the last as a sec-butyl ether (R=CH3) would give a strong m/e 45 peak. Thus a t least one ether group is a tert-butyl. This would also account for the strong 115 ion by the beta cleavage mechanism. The Fveaker mass 87 peak can arise b y beta cleavage of either an nor isobutyl ether. The spectrum is actually that of isobutyl tert-butyl ether, though the mass spectrum cannot definitely rule out n-butyl, tert-butyl, or di-tert-butyl ether without the reference spectrum of the knoll-n compound.
+
+
+
89, Methyl fert-Butyl Ether (Mol. Wt. 88)
Peak Height w t ., Drawout, Volts m / e 73 mle 87 m / e 89 M g. 5 .O 3.0 2.0a 5020 18.05 10.3 13.6 8780b 2.0 40.8 12.0 22.6 8840b 2.0 68.7 5.7 13.T 1.0 4200 65.7 0.4 2.1 450 0.0 68.7 Normal instrument operating parameters. Drop in sensitivity due to pressure broadening of peaks.
1788 *
STRUCTURE DETERMINATION
+
H H
a
+
+
served a similar JI 41 ion (M CH3CK?), nhile a large number of anomalous peaks above the molecular weight have been observed in the spectra of various hydrocarbons (15, 19).
Alpha and Beta Cleavage with Hydrogen Rearrangement
89/87
0.6 1.3 1.9 2.4 5,O
MECHANISM
Initial ionization probably takes place by loss of one of the nonbonding electrons of the oxygen atom under electron bombardment. Similar charge localization has been postulated for the analogous oxygen atom in alcohols ( 7 , 11). R:O:R/
+e
+
R:O:R/+
+ 2e
For alpha cleavage, rupture probably occurs here because the lowered electron density around the oxygen atom weakens a C-0 bond. R:O:R‘- + ~
.
i
j
:
+. ~ rR+ ~
+ .O:R~
The balanced inductive effects of symmetrical ethers and the absence of re-
Table VI. Use of Method m / e 131 Relative abundance changes with sample pressure and ion drawout voltage m / e 130 0.03% CnH?n+l CnHzn+10 m/e % m/e % mle 70 PC, 10 31 2 87 4.0 45 1 43 5 101 0.1 59 411 57 100 115 15.0 71 1 73 1 129 0.2
active bonds in n-alkyl groups probably contribute t o the prominence of alpha cleavage in these types of molecules. The unbalanced inductive effect could also account for the lack of this mode of degradation in alcohols and primary amines. If the positive charge went to the OR’group instead of the alkyl, it would leave only six electrons around the oxygen atom. For beta cleavage, the mechanism proposed b y Cummings and Bleakney ( 7 ) for ethyl alcohol can be extended to the ethers:
electron (stable) product ion and molecule. However, without the rearrangement shown such products would be R2C=0 and CZH6+, requiring shifting of the positive charge localized on the oxygen atom in the original ion. An alternative mechanism could involve a n initial breakdown to the alcohol ion and alkene molecule with hydrogen rearrangement. The preferred mode of cleavage in the spectra of such alcohols is at the beta bond, which would then yield the -R,’COH ion. R‘ R-COCH~CH~R~’ + ,
R.
+
H C: *. :O:R’+ .. H
The larger the R’ group, the more its electron-donating polyer mill neutralize the lost electron on the oxygen atom. This will then lower the porrer of the oxygen t o attract the electron of the R-C bond. Thus the greatest tendency for beta cleavage should be found where R’ = H or CH3-i.e., alcohol or methyl ether. For the alpha and beta cleavage with hydrogen rearrangement, a mechanism may be postulated that yields first a fragment ion from beta cleavage of the labile secondary or tertiary bond, as discussed above. Loss of the stable alkene molecule CH2=CHR”, with rearrangement of a hydrogen atom yields the R2’COH ion. R’ H H R:C:O:C:C:R”+
.. .. .. ..
R’
-
H H R.
R‘
R’
H H
Rf
HH
+ 6: .. :O:C:C:R”+ ..
‘*“
R‘ R’
R‘
I I
R-COH+
+ CHz=CHR”
R’
Primary alcohols add chemically to reactive olefins-e.g., RzC=CH2-to give ethers ( 8 ) , the reverse of the first step. However, the attraction of the oxygen for rearranging hydrogen atom is probably less in this second mechanism than that of the first, where the oxygen is in a radical ion. A concerted mechanism is also possible in which the electron-deficient oxygen simultaneously attracts in a n electron from a beta bond and a hydrogen radical from the opposite beta carbon atom, with resulting loss of the alkyl radical by beta bond cleavage and the opposite alkene molecule b y alpha bond rupture. Migration of the alpha hydrogen atom cannot be ruled out, b u t appreciable rearrangement does not take place when only alpha hydrogens are available. There are other cases in which rearrangement of the hydrogen beta to the ruptured bond is postulated (11,IS, 17).
H
..
C .. : : O : H +
’
I
R‘
+ C: : C : R ” H H
Decomposition of the even-electron R2‘COCZH4R’’* ion would be strongly favored by formation of the even-
ACKNOWLEDGMENT
The author wishes to acknowledge very helpful discussions on various points of this paper with R. S. Gohlke, A. L. Wahrhaftig, 8. W. Baker, and
H. H. Freedman. E. 0. Camehl tabulated many of the data. LITERATURE CITED
(1) Am. Petroleum Inst., API Project 44, Catalog of Mass Spectra, Carnegie Institute of Technology, Pitts-
burgh, Pa. (2) Beynon, J. H., Imperial Chemical Industries, Ltd., Llanchester, England, private communication. (3) Caldecourt, V. J., ASTM E-14 Meeting on Mass Spectrometry, Xew Orleans, May 1954. (4) Collin, J., Bull. soc. chim. Belg. 63, 500 (1954). (5) Collin, J., Bull. Soc. Roy. Sei. Liege 21, 446 (1952). (6) Ibid., 23, 377 (1954). (7) Cummings, C. S., Bleakney, IT., Phus. Rev. 58. 787 (1940). (8) Evans, T. W.,Edlund, K. R., Ind. Eno. Chem. 28, 1186 (1936). (9) Friedkl, R. A , , Sharlrey, A. G., Jr., A s . 4 ~ .CHEM.28, 940 (1956). (10) Friedel, R. ii.,Shultz, J. L., Sharkey, A. G., Jr., Zbid., 28, 926 (1956). (11) Friedman, L., Turkevich, J., J . Am. Chem. Soc. 74, 1666 (1952). (12) Gilpin, J. A., McLafferty, F. W., A X A L . CHEX., 29, 990 (1957). (13) Gohlke, R. S., McLafferty, F. IT-., Division of Gas and Fuel Chemistrr. 127th hleetim. -, ACS. Cinciniati, April 1955. (14) Gohlke, R. S., McLafferty, F. W., unpublished work. (15) Hinkle, E. A,, Roberts, G. L., Haniner, IT. F., ASTM E-14 Meeting on Mass Snectrometrv. ” , Cincinnati. Slav 1956: (16) Judson, C. AI., Francel, R. J., ASTM E-14 Meeting on Mass Spectrometrv. San Francisco. Mav 1955. (17) McLafferty, F. W., - ~ & A L .~ H E I I .28, 306 (1956). (18) McLafferty,‘ F. W,,Dow Chemical Co.. Tech. Reut.. Kovember 1955. (19) Schissler, D. 0.; Stevenson, D. P., J . Chem. Phyls. 24, 926 (1956). Stevenson, D.- P., Schissler, D. O., Ibid., 23, 1353 (1955). Tal’roze. V. L.. Lvubimova. A. K.. Doklady Akad. hrauk S.S.R. 86; 906 (1952). Taylor, R. C., Brown, R. A., Young, W.S., Headington, C. E., ANAL. CHEM.2 0 , 396 (1948). Wertzler, R., Kinder, J. F., Consolidated Engineering Corp., Pasadena, Calif., Group Rept. 54 (July 1948). RECEIVED for review March 29,1957. Accepted August 21, 1957. ASTM E-14 Committee Meeting on Mass Spectrometry, Cincinnati, May 1956. VOL. 29, NO. 12, DECEMBER 1957
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