The NMR spectrum of anthranil oriented in a nematic phase

Journal of Molecular Structure, Elsevier Science Publishers B.V

117

(1984)

, Amsterdam

157-159 - Prmted

IX-IThe Netherlands

Short communication

THE NMR PHASE

SPECTRUM

OF AN-THRANIL

ORIENTED

IN A NEMATIC

S ARUMUGAM Indian Institute A

C

of Science,

KUNWAR

Raman

Research

(Received

andC

L

Instrtute,

21 November

Bangalore

560012

(Indra)

KHETRAPAL* Bangalore

560080

(Indza)

1983)

A large number of bicycle systems containing a five-membered ring fused to a srx-membered nng have been mvestigated by ‘H NMR spectroscopy liqurd crystal solvents [l, 21. As a contmuatlon of our studies on benzo(b)furan and benzo(b)thiophene [3, 4] we present herein results for anthraml (2,1-benzisoxazole) which has two heteroatoms, namely nitrogen and oxygen in the five membered ring, and has been shown to have antiulcer activity [5] . The NMR experiments were performed on a Bruker WH-270 spectrometer_ A solution of about 6 mol% of anthranll in a murture of 69 mol per cent N-@‘-methoxybenzyhdene)-p-n-butylamlme (MBBA) and 31 mol per cent N-(p’-ethoxybenzylidme)-p-n-butylamlme (EBBA) was studred at 20.5”C. Thirty srx free mductron decays were accumulated and Founer transformed with 16K data pomts on a BNC-12 computer with 20K memory. The average lmewldth was about 4 Hz. The spectral analysis was carned out wrth the help of the LEQUOR program [6] on a DEC-1090 computer_ Durmg the fmal analysis iterations were carried out on the chemical shifts (vZ) and the duect dipole-dipole couplings (DIJ) between the interactmg nuclei z and]. The mdlrect couplmgs (J,) taken from the literature [ 71 were kept fixed. The fmalset of parameters obtamed after assigning 105 lmes to a r.m.s. error of 0.22 Hz are given m Table 1. The errors of the parameters correspond to those obtained from the LEQUOR program. Because of the presence of the plane of symmetry, the complete defmltlon of the shape of the proton skeleton can be described by six ratios of the inter-proton distances (r,,) and the molecular onentation could be specrfied by three order parameters (S,,). A weighted least-square fit program SHAPE [S] has been used to obtam the structural and orientatronal parameters reported in Table 1 horn the ten dlpolar couplings. The dipolar couplmgs *Author

to whom

0022-2860/84/$03

all correspondence 00

o 1984

should Elsevier

be addresed Science

Publishers

B.V

158 TABLE

1

Spectral, geometrical and order mixture of MBBA and EBBAa Parameter

D,,

Value -634.05 -118.17 -38.48

D,, D,.? D1,

parameters

(Hz) f 0.04 * 0 12 c 0 09

2 36 + 0.09 -574.35 + 0.12 23.60 + 0.08 23 82 * 0 07 205.31 + 0.06 -78.22 + 0.09 -1134.39 + 0.03 488.38 5 0.16 589.60 + 0.04 538.242008 467.38 5 0.09

D,, D,, DZ, D,, D,, D,, vl-“I “>_“I “4-y* “5-Y,

for Anthraml

from

the NMR

spectrum

Parameter

Value

rr 11r34 ‘l,l’N r14lr34

1.287 2.146 2.487

r15lr34

2 226*0006

rzJ Jrs4 r14fr34 r&r4 r,,lr,, r45lr35 p; s:> Sxyh

in the

f 0 003 c 0.004 t 0.004

1.008 t 0 001 1751 c 0.001 2 060 i 0.004 1.757 -F 0.003 1007 * 0.001 01633~00009 -0 0261* 0.0001 0 1372 -0 0418 i 0.0004

=Indirect couplings used [7] J,, = -0.05, J,, = 0.04, J,, = -0.04, J,, = 0_99,J,, = 0_93,J,, = 6.72, J,, = 0.76, J,, = 8.70 Hz. bThe

J,, = 1.09, Jzo = 8.66, rrght handed Cartesian coordinate system used has the XY plane as the molecular plane of symmetry wrth the positive Y-axis as the one obtained by joimng proton 4 to proton 3- rs4 = 2.481 ii (assumed)

were given the weights correspondmg to the inverse of their errors quoted in Table 1. It can be seen from Table 1 that the phenyl ring has fairly large distortions from a regular hexagonal geometry; they are similar in magnitude to those in benzo(b)furan [4] and some asymmetric di- and tnazanaphthalenes investigated recently [9]_ It is also obsemed that the value of 1.287 for r1JrS4 in anthranil is larger than that in benzo(b)furan (1.099). This 13in accord with the bond polarization hypothesis [lo] according to which the CH( 1) bond is attracked towards the oxygen in anthranil thereby increasing the distance between protons 1 and 2. A similar effect is observed for the CH(5) bond in anthranil which results in the increase of the distance between protons 4 and 5 such that 7h5/rS4is greater than 1.000. Y

Z’

Anthranil orients preferentially with its long axis along the field direction like most of the other bicycle systems [I, 21. The principal axes of the ordering makix tensor are inclined by -11.9” with respect to the Cartesian coordinate system used in the present study.

159

ACKNOWLEDGEMENT

S. A. gratefully ment of India.

acknowledges

the financial support from D. A. E., Govem-

REFERENCES 1 C L Khetrapal and A. C. Kunwar, m J W Wangh (Ed ), Advances u-rMagnetic Resonance, Vol. 9, Academrc Press, New York, 1977, pp. 301-422. 2 C. L Khetrapal and A. C Kunwar, in G H. Brown (Ed ), Advances m Liquid Crystals, Vol. 6, Academic Press, New York, 1983, pp 173-242. 3 S. Arumugam, A_ C. Kunwar and C. L. Khetrapal, Org. Magn. Reson., 18 (1982) 157 4 C L. Khetrapal, A. C. Kunwar and A_ Saupe, Pramana, Suppl No. 1, (1975) 495. 5 P Manolov and S. Todorov, Eksp. Med. Morfol , 13 (1974) 36. 6 P. Diehl, H. P. Kellerhals and W. Niederberger, J Magn. Reson , 4 (1971) 352 7 K H. Wunsch and A. J. Boulton, m A R Katrrtzky and A J Boulton (Eds ), Advances in Heterocyclic Chemistry, Vol. 8, Academic Press, New York, 1967, pp 277- 379 8 P Derhl, P M. Henrichs and W. Niederberger, Mol. Phys , 20 (1971) 139 9 S Arumugam, A. C. Kunwar and C. L. Khetrapal, unpublished results 10 C L Khetrapal and E D. Becker, J. Magn Reson , 43 (1981) 8