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The influence of N-substituents on the ring proton shifts in aziridines
Tetmhedrm.
Vd
26. pp. 227 to 232
Pcrpmon
Rem
1970.
Printed in Great Britain
THE INFLUENCE OF N-SUBSTITUENTS ON THE RING PROTON SHIFTS IN AZIRIDINES’ THE ROLE OF MAGNETIC ANISOTROPY AND INTRAMOLECULAR DISPERSION EFFECTS:
S.J. BROIS Esso Resmrch and
Engineering Company, Linden, New Jersey
(Received in U.S.A. 22 June 1969; Received in the UKfor publication 9 September 1969) --The effect of N-alkyl substituents on the ring proton shifts in axiridines is reported. We have found that ring protons cis to the magnetically anisotropic N-alkyl bond show a chemical shift to higher field The magnitude of the shielding effect tends to decrease with the steric requirements of the N-substituent, ie, Me > Et > i-Pr N t-Bu. The observed trend in deshielding has been ascribed to intramolecular van der Waals (dispersion) interactions between the N-alkyl and cis ring protons A dispersioninduced deshielding and shielding (DIDS) effect has been invoked to account for the ring proton shifts in sterically crowded axiridines such as 1-t-butylstyrenimine and I-t-butylaziridine.
IN A recent study’ of vicinal proton couplings in the configurationally pure cis isomers, A and B, we found that the benxylic proton (HA in B was shifted ca 075 ppm upfield relative to H, in A. Initially, we proposed* that the magnetically anistropic N-methyl C-N bond shielded the cis protons, i.e., H, and H, in the more stable tiuns conformation shown below. R A B
H Me
In contrast to our proposal, however, Turner et al.* had recently suggested that the lower geld absorptions in the ring proton spectra of l-alkyl-2,3dibenxoylaziridines were due to the ring protons cis rather than ZTMSto the substituent on nitrogen. In view of these conflicting claims, we undertook a more thorough investigation to elucidate the role that N-substituents played in determining ring proton shifts in aziridines The present communication describes the remarkable effect that N-alkyl groups exert on ring proton shifts in styrenimines (2-phenylaziridines) and ethylenimines (aziridines). RESULTS
AND
DISCUSSION
l-Me, l-Et, 1-i-Pr, and 1-t-Bu analogs of styrenimine and axiridine were prepared according to the Wenker procedure.5*6 The proton spectra of styrenimines The
l After completion of our work,’ Bystrov et ol.’ reported in harmony with our proposal, that the diamagnetic anistropy of the N-R bond exerts a stronger e5ect on the cis ring protons.
227
S. J. Boors
228
I-V and aziridines VI-X were recorded at room temperature as 10 and 50% (w/w) CC14 solutions, and as a soo/, cyclohexanediz (w/w) solution. The ring proton spectra for the five styrenimin es (I-V) as 500/, CCl, solutions are illustrated in Fig 1. In the spectrum of III, the second line of the H, signal is masked by the outer line of the N-methylene signal. Solvent and concentration effects did not appear to significantly alter the relative chemical shifts attributed to intramolecular contributions. In general, first order spectra are observed for these unsymmetrical 3-spin systems and accordingly, each case was treated as a simple ABX system as previously described.’ The assignment of bands was based on the assumption that J,,, > J, in harmony with our earlier studies2 Ring proton coupling constants for the styrenimines are recorded in Table 1. Within the framework of current theory,s the similarity of the geminal and vicinal proton coupling constants for I-V suggests that any substituent-induced changes in the ring geometry of these molecules are essentially negligible. TABLB 1. G-AL
AND VIClNAL
I II III IV V l
PRMON
COUPLINQ
CmJSTANIYi
POR
.WYRJMMlNE¶’
J,
Jbr
Jab(c/s)
6.2 6.4 6.4 64 6.3
3.3 32 3.2 3.2 2.8
09 1.3 1.2 l-2 1.4
As so”/, CCl, solns at room temp.
A careful inspection of Fig 1 and Table 2 reveals the remarkable effect that Nsubstituents exert on the chemical shifts of the ring protons in aziridines II-V. Contrary to an earlier claim,4 we find that the ring protons cis to N-alkyl substituents show a chemical shift to higher field. Moreover, the magnitude of the shielding effect tends to decrease with the steric requirements of the N-substituent, i.e., Me > Et > i-Pr $ t-Bu. The observed trend in the ring proton shifts is surprising since one would have
styreniminc
I II III IV V
H, ccl.*
GD,z’
1638 123.2 127.2 lW5 149.6
162.3 122.3 125.8 130.0 1496
’ In c/s from internal TMS. * As WA ccl. solns (w/w). ’ As 50% C6D,, solns (w/w).
Hb
H.
C& 112.4 808 83-8 868 104.3
C6h
1108 78.7 81-8 85.2 103.4
ca
87-4 99.4 99.4 99.4 869
CsD12
849 97.3 972 97.2 84.3
Tk iafluencc of N-substitucnts on the ring proton shiftsin aziridines
L 170
150
130
110
229
90
c/s from internal l-MS FIG. 1 Ring
proton spectra of stymimincs as 50% cci.
solutions (100 c/s sweep width).
expeuted &reused shielding from the anisotropy of the N-alkyl C-C single bondsmg At present, we theorize tbat such deshiclding is ascribable to intramokcular Van der Waals (dispersion) interactions lo between the N-alkyl and ring (H, and HJ protons. It appears that the inverting N-alkyl and ring protons come into such close proximity that strong dispersion interactions occur. Presumably, the nonbonded interactions between the ring and N-alkyl hydrogen5 cause a distortion of the electron cloud around the compressed ring protons and
S. J. BROIS
VI
VII
90
80
70
60
50
C/s from internalTMS Fw. 2 Ring proton spectra of l-alkyhziridinca aa soo/, CCl, solutions. The assignment of peaks in X is provisional.
deshielding of the latter cccurs. As indicated above, such dispersion effects become especially important as the steric requirements of the N-aIky1 group increase. Thus the Van der WaaIs contribution to 6 I-I. and 6 H, in the lethyl and l-isopropylstyrenimine relative to the l-Me analog is as expected, rather small On the other hand, the steric deshielding effect on I-I, and H, due to the bulky t-Bu group in V is remarkable. Significantly, van der Waals shifts of similar magnitude have also been observed’ ’ for the ring protons in 1-alkylaziridines (VIII-X). The proton spectra (Figure 2) and vAt,values (Table 3) for the 1-alkylaxiridines clearly illustrate this point. In addition,
The influence of N-substituents on the ring proton shifts in axiridines
231
TABLE3. v*s VALUFSFOR I-ALKYLAZIRIDINES’ R
vAil 0
Me
42 39 36 3b
7
Et i-Pr t-Bu
’ 6@Mc/s spectra recorded as SoO/,CCI, solutions. b Peak separation.
note that the strong dispersion forces associated with the bulky t-Bu group in X appear to alter the magnetic environment of the cis (H,) and (H,,) protons. The dispersion-induced deshielding and shielding (DZDS)e&cc. Especially germane to the mechanism of dispersion effects in aziridines is the observation that H, in l-t-butylst~enimine (V) and 1-t-butyl~~dine (X) is shifted over 02 ppm to higher field relative to H, in the corresponding N-Me, N-Et and N-i& analogs. We conjecture that this diamagnetic shift reflects further distortion of the ring proton electron cloud by the sterically demanding t-Bu group. Apparently, the distorted electron cloud of the ring protons is shifted away from the cis protons towards the other plane of the ring, thus accounting for the deshieiding of the compressed protons and higher shielding of H, in aziridines V and X. At present, we propose that the NMR spectral data for such sterically crowded aziridines as typified by 1-t-butylaziridine and 1-t-butylstyrenimine can be most easily rationalized in terms of a dis~rsion-indu~ deshieiding and shielding (DIDS) effect. We are currently seeking to magnify the DIDS effect in model aziridines with more stericallydemanding substituents of varying electronegativities (12). EXPERIMENTALt Aziridine synthesis. The styrenimines I-V and aziridines VI-X were prepamd according to tbc proceduredescribed by Brois.’ Physical, yield and analytical data for the styrenimines are depicted in Table 4. The aziridinesVI-X were previously reported.5b NMR spectra. The proton spectra of styrenimines I-V and axiridines VI-X as 10 and SOD/,CC& solns (w/w) and as 50% cyclohexanc-d,x solution (w/w) were determined at room temp employing a Varian A-60 spectrometer. chemical shift values were obtained in each case l&n replicate spectra run at a sweep width of 100 c/s. REFERENCES
’ Presented in part at the 153rd National Meeting of the American Chemical Society, Abstracts pp. 72-80. Miami Beacb, Florida, April 9 (1967). 2 S. 1. Brois and G. P. BeardsIcy, Terrtiedron Letters 5113 (1966). ’ V. F. Bystrov, R. G. Kostyanovskii, 0. A. Panshin, A. V. Stepanyants, and 0. A Inxbakova, i&r i Spxtry USSR 19,217 (1965); transl Optics A. Spectroscopy 19, 122 (lW5). * The remarkable chemical shift trend recently observed lo1 for the ring protons in sterically crowded half-cage molecules represents a classic example of the DIDS e&t_ t Bps are uncorrected, IR spectra of neat liquid samples wem determined with a Perkin-Elmer Model 21 spedrophotometer with NaCl optics The NMR spaztra were run at room temp employing a Varian Model A-60 spectrometer. Gas chromatographic analyses were obtained witb an F B M Scientific Corp. Model 500 linear programmed temp gas chromatograpb Microanalyses were performed by Schwarzkopf Microanalytical Laboratory, Woodside 77. New York.
232
S. J. BROIS
’ A. B. Turner, H. W. Heine, J. Irvin& and J. B. Bush, Jr., J. Am. Gem. Sot. 87,105O (1965). ’ ’ S. J. Brois, 1. Org. Gem. 27.3532 (1962); * Ph.D. Thesis, Univ. of Chica (1960). 6 J. N. Wells, A. V. Shhdkar, and A. M. Kncvel, .I. Med. Chem 9,195 (1966). ’ S. L. Manatt, D. D. Elleman and S. J. Brois, 1. Am. Chem. SUC.87.2220 (1965). * M. Kqlus,
Ibid. 85.2870
(1963).
’ A A. Bother-By and C Naar-Colin, Ibid 83,231(1961); 812784 (1962); F. k Bovey and F. P. Hood, III. Ibid. 87,20&l (1965). lo . C. Reid, J. Mol. Spectry, l, 18 (1957); b T. Schaefer, W. F. Reynolds and T. Yoncmoto, &I. 1. Char. 4l, 2969 (1963); c R. J. Abraham and J. S. E Holkcr, J. Gem. Sue. 806 (1963); ’ K. Tori and K. Kuriyama, Chem. & hf. 1525 (1963); ’ V. M. S. Gil and W. A. Gibbons, Mol. Phys. 8,199 (1964); 1 W. Nagata, T. Tcrisawa and K. Tori, J. Am. Chem_Suc. 86,3746 (1964); ’ E. M. Arnctt and J. N. Bollin8q Ibid, 864729 (1964); h N. Boden, J. W. Em&y, J. Feeney aml L H. Sutcliffe, MoL Phya 8,133 (1964); ’ S. Winutcin, P. Carter, F. A. L. Anet and A. J. R. Bourn, J. Ant Ghan Sot. 87,5247 (1965); ’ K. Tori and T. Komcno, Tetrahedr~ 2% 309 (1965); t D. R. Arnold, D. J. Treckcr and E. B. Whipple, 1. Am Chem Sot. 87,25% (1965); ’ M. A. Battiste and M. E Brcmuxn, Tetrahedral Letters 5857 (1966); - T. Yoncmoto, Can. J. Gem. 44,223 (1966); ” R. L. Van Etten, Mss. Absrr. 26(S), 4250 (1966); l T. H. Regan and J. B. Miller, J. Org. Chem 32,2789 (1967) and r&nmcea cited therein. I1 S. J. Brois, J. Am Chem Sot. B9,4242 (1967). I2 S. J. Brois, Ibid, 90,506 (1968); Tetrahedron Letters,5997 (1968)
TALLY 4. YlL&DSANDPHYSICAL Yield Aziridine
%
DATA
FOR -
B.p. “C (mm)
C
H
N
I
90
94-95 (10)
1.5588
8@62 8075
7.61 7.79
11.76 Theory 11.50 Found
II’
76
3940
(05)
1.5327
81.16 81.36
8.33 S.tXI
1052 1044
III’
82
4142
(01)
1.5220
81.58 81.58
890 8.93
952 955
IVC
87
315-32 (005)
1.5087
81.93 81.88
9.38 9,75
8.69 8.75
V
75
65-66 (@65)
15070
82.23 82Ql
978 993
799 8.tXl
’ Ref. 7 reports b.p. 35-37” (03 mm), 4’ 1.5321. b Ref. 7 r&ts b.;. &70” (2.5 mm), la” 1.5220. c Ref. 7 reports b.p. 68-70” (2.4 mm), do 15O!X).
Vd
26. pp. 227 to 232
Pcrpmon
Rem
1970.
Printed in Great Britain
THE INFLUENCE OF N-SUBSTITUENTS ON THE RING PROTON SHIFTS IN AZIRIDINES’ THE ROLE OF MAGNETIC ANISOTROPY AND INTRAMOLECULAR DISPERSION EFFECTS:
S.J. BROIS Esso Resmrch and
Engineering Company, Linden, New Jersey
(Received in U.S.A. 22 June 1969; Received in the UKfor publication 9 September 1969) --The effect of N-alkyl substituents on the ring proton shifts in axiridines is reported. We have found that ring protons cis to the magnetically anisotropic N-alkyl bond show a chemical shift to higher field The magnitude of the shielding effect tends to decrease with the steric requirements of the N-substituent, ie, Me > Et > i-Pr N t-Bu. The observed trend in deshielding has been ascribed to intramolecular van der Waals (dispersion) interactions between the N-alkyl and cis ring protons A dispersioninduced deshielding and shielding (DIDS) effect has been invoked to account for the ring proton shifts in sterically crowded axiridines such as 1-t-butylstyrenimine and I-t-butylaziridine.
IN A recent study’ of vicinal proton couplings in the configurationally pure cis isomers, A and B, we found that the benxylic proton (HA in B was shifted ca 075 ppm upfield relative to H, in A. Initially, we proposed* that the magnetically anistropic N-methyl C-N bond shielded the cis protons, i.e., H, and H, in the more stable tiuns conformation shown below. R A B
H Me
In contrast to our proposal, however, Turner et al.* had recently suggested that the lower geld absorptions in the ring proton spectra of l-alkyl-2,3dibenxoylaziridines were due to the ring protons cis rather than ZTMSto the substituent on nitrogen. In view of these conflicting claims, we undertook a more thorough investigation to elucidate the role that N-substituents played in determining ring proton shifts in aziridines The present communication describes the remarkable effect that N-alkyl groups exert on ring proton shifts in styrenimines (2-phenylaziridines) and ethylenimines (aziridines). RESULTS
AND
DISCUSSION
l-Me, l-Et, 1-i-Pr, and 1-t-Bu analogs of styrenimine and axiridine were prepared according to the Wenker procedure.5*6 The proton spectra of styrenimines The
l After completion of our work,’ Bystrov et ol.’ reported in harmony with our proposal, that the diamagnetic anistropy of the N-R bond exerts a stronger e5ect on the cis ring protons.
227
S. J. Boors
228
I-V and aziridines VI-X were recorded at room temperature as 10 and 50% (w/w) CC14 solutions, and as a soo/, cyclohexanediz (w/w) solution. The ring proton spectra for the five styrenimin es (I-V) as 500/, CCl, solutions are illustrated in Fig 1. In the spectrum of III, the second line of the H, signal is masked by the outer line of the N-methylene signal. Solvent and concentration effects did not appear to significantly alter the relative chemical shifts attributed to intramolecular contributions. In general, first order spectra are observed for these unsymmetrical 3-spin systems and accordingly, each case was treated as a simple ABX system as previously described.’ The assignment of bands was based on the assumption that J,,, > J, in harmony with our earlier studies2 Ring proton coupling constants for the styrenimines are recorded in Table 1. Within the framework of current theory,s the similarity of the geminal and vicinal proton coupling constants for I-V suggests that any substituent-induced changes in the ring geometry of these molecules are essentially negligible. TABLB 1. G-AL
AND VIClNAL
I II III IV V l
PRMON
COUPLINQ
CmJSTANIYi
POR
.WYRJMMlNE¶’
J,
Jbr
Jab(c/s)
6.2 6.4 6.4 64 6.3
3.3 32 3.2 3.2 2.8
09 1.3 1.2 l-2 1.4
As so”/, CCl, solns at room temp.
A careful inspection of Fig 1 and Table 2 reveals the remarkable effect that Nsubstituents exert on the chemical shifts of the ring protons in aziridines II-V. Contrary to an earlier claim,4 we find that the ring protons cis to N-alkyl substituents show a chemical shift to higher field. Moreover, the magnitude of the shielding effect tends to decrease with the steric requirements of the N-substituent, i.e., Me > Et > i-Pr $ t-Bu. The observed trend in the ring proton shifts is surprising since one would have
styreniminc
I II III IV V
H, ccl.*
GD,z’
1638 123.2 127.2 lW5 149.6
162.3 122.3 125.8 130.0 1496
’ In c/s from internal TMS. * As WA ccl. solns (w/w). ’ As 50% C6D,, solns (w/w).
Hb
H.
C& 112.4 808 83-8 868 104.3
C6h
1108 78.7 81-8 85.2 103.4
ca
87-4 99.4 99.4 99.4 869
CsD12
849 97.3 972 97.2 84.3
Tk iafluencc of N-substitucnts on the ring proton shiftsin aziridines
L 170
150
130
110
229
90
c/s from internal l-MS FIG. 1 Ring
proton spectra of stymimincs as 50% cci.
solutions (100 c/s sweep width).
expeuted &reused shielding from the anisotropy of the N-alkyl C-C single bondsmg At present, we theorize tbat such deshiclding is ascribable to intramokcular Van der Waals (dispersion) interactions lo between the N-alkyl and ring (H, and HJ protons. It appears that the inverting N-alkyl and ring protons come into such close proximity that strong dispersion interactions occur. Presumably, the nonbonded interactions between the ring and N-alkyl hydrogen5 cause a distortion of the electron cloud around the compressed ring protons and
S. J. BROIS
VI
VII
90
80
70
60
50
C/s from internalTMS Fw. 2 Ring proton spectra of l-alkyhziridinca aa soo/, CCl, solutions. The assignment of peaks in X is provisional.
deshielding of the latter cccurs. As indicated above, such dispersion effects become especially important as the steric requirements of the N-aIky1 group increase. Thus the Van der WaaIs contribution to 6 I-I. and 6 H, in the lethyl and l-isopropylstyrenimine relative to the l-Me analog is as expected, rather small On the other hand, the steric deshielding effect on I-I, and H, due to the bulky t-Bu group in V is remarkable. Significantly, van der Waals shifts of similar magnitude have also been observed’ ’ for the ring protons in 1-alkylaziridines (VIII-X). The proton spectra (Figure 2) and vAt,values (Table 3) for the 1-alkylaxiridines clearly illustrate this point. In addition,
The influence of N-substituents on the ring proton shifts in axiridines
231
TABLE3. v*s VALUFSFOR I-ALKYLAZIRIDINES’ R
vAil 0
Me
42 39 36 3b
7
Et i-Pr t-Bu
’ 6@Mc/s spectra recorded as SoO/,CCI, solutions. b Peak separation.
note that the strong dispersion forces associated with the bulky t-Bu group in X appear to alter the magnetic environment of the cis (H,) and (H,,) protons. The dispersion-induced deshielding and shielding (DZDS)e&cc. Especially germane to the mechanism of dispersion effects in aziridines is the observation that H, in l-t-butylst~enimine (V) and 1-t-butyl~~dine (X) is shifted over 02 ppm to higher field relative to H, in the corresponding N-Me, N-Et and N-i& analogs. We conjecture that this diamagnetic shift reflects further distortion of the ring proton electron cloud by the sterically demanding t-Bu group. Apparently, the distorted electron cloud of the ring protons is shifted away from the cis protons towards the other plane of the ring, thus accounting for the deshieiding of the compressed protons and higher shielding of H, in aziridines V and X. At present, we propose that the NMR spectral data for such sterically crowded aziridines as typified by 1-t-butylaziridine and 1-t-butylstyrenimine can be most easily rationalized in terms of a dis~rsion-indu~ deshieiding and shielding (DIDS) effect. We are currently seeking to magnify the DIDS effect in model aziridines with more stericallydemanding substituents of varying electronegativities (12). EXPERIMENTALt Aziridine synthesis. The styrenimines I-V and aziridines VI-X were prepamd according to tbc proceduredescribed by Brois.’ Physical, yield and analytical data for the styrenimines are depicted in Table 4. The aziridinesVI-X were previously reported.5b NMR spectra. The proton spectra of styrenimines I-V and axiridines VI-X as 10 and SOD/,CC& solns (w/w) and as 50% cyclohexanc-d,x solution (w/w) were determined at room temp employing a Varian A-60 spectrometer. chemical shift values were obtained in each case l&n replicate spectra run at a sweep width of 100 c/s. REFERENCES
’ Presented in part at the 153rd National Meeting of the American Chemical Society, Abstracts pp. 72-80. Miami Beacb, Florida, April 9 (1967). 2 S. 1. Brois and G. P. BeardsIcy, Terrtiedron Letters 5113 (1966). ’ V. F. Bystrov, R. G. Kostyanovskii, 0. A. Panshin, A. V. Stepanyants, and 0. A Inxbakova, i&r i Spxtry USSR 19,217 (1965); transl Optics A. Spectroscopy 19, 122 (lW5). * The remarkable chemical shift trend recently observed lo1 for the ring protons in sterically crowded half-cage molecules represents a classic example of the DIDS e&t_ t Bps are uncorrected, IR spectra of neat liquid samples wem determined with a Perkin-Elmer Model 21 spedrophotometer with NaCl optics The NMR spaztra were run at room temp employing a Varian Model A-60 spectrometer. Gas chromatographic analyses were obtained witb an F B M Scientific Corp. Model 500 linear programmed temp gas chromatograpb Microanalyses were performed by Schwarzkopf Microanalytical Laboratory, Woodside 77. New York.
232
S. J. BROIS
’ A. B. Turner, H. W. Heine, J. Irvin& and J. B. Bush, Jr., J. Am. Gem. Sot. 87,105O (1965). ’ ’ S. J. Brois, 1. Org. Gem. 27.3532 (1962); * Ph.D. Thesis, Univ. of Chica (1960). 6 J. N. Wells, A. V. Shhdkar, and A. M. Kncvel, .I. Med. Chem 9,195 (1966). ’ S. L. Manatt, D. D. Elleman and S. J. Brois, 1. Am. Chem. SUC.87.2220 (1965). * M. Kqlus,
Ibid. 85.2870
(1963).
’ A A. Bother-By and C Naar-Colin, Ibid 83,231(1961); 812784 (1962); F. k Bovey and F. P. Hood, III. Ibid. 87,20&l (1965). lo . C. Reid, J. Mol. Spectry, l, 18 (1957); b T. Schaefer, W. F. Reynolds and T. Yoncmoto, &I. 1. Char. 4l, 2969 (1963); c R. J. Abraham and J. S. E Holkcr, J. Gem. Sue. 806 (1963); ’ K. Tori and K. Kuriyama, Chem. & hf. 1525 (1963); ’ V. M. S. Gil and W. A. Gibbons, Mol. Phys. 8,199 (1964); 1 W. Nagata, T. Tcrisawa and K. Tori, J. Am. Chem_Suc. 86,3746 (1964); ’ E. M. Arnctt and J. N. Bollin8q Ibid, 864729 (1964); h N. Boden, J. W. Em&y, J. Feeney aml L H. Sutcliffe, MoL Phya 8,133 (1964); ’ S. Winutcin, P. Carter, F. A. L. Anet and A. J. R. Bourn, J. Ant Ghan Sot. 87,5247 (1965); ’ K. Tori and T. Komcno, Tetrahedr~ 2% 309 (1965); t D. R. Arnold, D. J. Treckcr and E. B. Whipple, 1. Am Chem Sot. 87,25% (1965); ’ M. A. Battiste and M. E Brcmuxn, Tetrahedral Letters 5857 (1966); - T. Yoncmoto, Can. J. Gem. 44,223 (1966); ” R. L. Van Etten, Mss. Absrr. 26(S), 4250 (1966); l T. H. Regan and J. B. Miller, J. Org. Chem 32,2789 (1967) and r&nmcea cited therein. I1 S. J. Brois, J. Am Chem Sot. B9,4242 (1967). I2 S. J. Brois, Ibid, 90,506 (1968); Tetrahedron Letters,5997 (1968)
TALLY 4. YlL&DSANDPHYSICAL Yield Aziridine
%
DATA
FOR -
B.p. “C (mm)
C
H
N
I
90
94-95 (10)
1.5588
8@62 8075
7.61 7.79
11.76 Theory 11.50 Found
II’
76
3940
(05)
1.5327
81.16 81.36
8.33 S.tXI
1052 1044
III’
82
4142
(01)
1.5220
81.58 81.58
890 8.93
952 955
IVC
87
315-32 (005)
1.5087
81.93 81.88
9.38 9,75
8.69 8.75
V
75
65-66 (@65)
15070
82.23 82Ql
978 993
799 8.tXl
’ Ref. 7 reports b.p. 35-37” (03 mm), 4’ 1.5321. b Ref. 7 r&ts b.;. &70” (2.5 mm), la” 1.5220. c Ref. 7 reports b.p. 68-70” (2.4 mm), do 15O!X).