organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
shown that, as a rule, PQs have dielectric indices exceeding
those of the famous DuPont `KAPTON' ®lm (Odnoralova &
Vasilyeva-Sokolova, 1978; Ponomarev et al., 1992; de Gaude-
maris et al., 1965).
ISSN 0108-2701
It is well known that when studying polymers, accurate
knowledge of the molecular structure of the corresponding
monomers is very important. For this reason, we undertook
the current X-ray stuctural analysis of three 2-substituted bis-
benzoxazinones, (I)±(III), which are of interest as PQ
precursors.
A series of three bis[2-(methyl/tri-
fluoromethyl)-4H-3,1-benzoxazin-4-
one] compounds
A. Yu. Kovalevsky* and I. I. Ponomarev
A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy
of Sciences, 28 Vavilov Str., Moscow 117813, Russia
Received 20 July 1999
Accepted 3 November 1999
0
Each of the three title compounds, namely 6,6 -methylene-
0
bis(2-methyl-4H-3,1-benzoxazin-4-one), C H N O , 6,6 -
1
9
14
2
4
methylenebis(2-tri¯uoromethyl-4H-3,1-benzoxazin-4-one),
0
C H F N O , and 6,6 -bi(2-tri¯uoromethyl-4H-3,1-benz-
1
9
8
3
2
4
oxazin-4-one), C H F N O , contains two planar benzox-
4
1
8
6
6
2
The three molecules display symmetry. Each molecule of
III) has a crystallographic inversion center which coincides
with the midpoint of the C6AÐC6A bond, whereas (I) and
II) each has a twofold axis passing through C11. The twofold
azinone fragments. In the ®rst two compounds, these planes
are virtually perpendicular to each other, while the third
compound is planar overall. The electronic effects of the
substituent groups on the oxazine moiety result in
(
i
(
symmetry is approximate (and non-crystallographic) in (I) but
crystallographic in (II). Furthermore, bond angles at C11 are
close to tetrahedral values in (I) (Fig. 1), but somewhat
distortion of the bond angles at the C atoms of the C
O
and C N bonds, and in redistribution of electronic density
in the oxazine rings. The latter leads to different bond
lengths within this ring in the three molecules. All the
i
distorted in (II) (Fig. 2), where the C6AÐC11ÐC6A bond
ꢁ
angle is 115.6 (4) .
molecules form stacks in their crystals with distances of
Ê
The benzoxazinone systems in all three molecules are
planar, in agreement with earlier experimental data (Etter et
al., 1982; Pink et al., 1993). Only in (III) does atom C10A of the
3
.2±3.6 A between adjacent molecules in a stack.
Comment
tri¯uoromethyl group deviate from the oxazine plane, by
Ê
0
.147 (2) A. There appears to be no obvious way to rationalize
Polyquinazolones (PQs, see scheme below) are an important
class of polyheteroarylenes which possess high thermal and
hydrolytic stability, and have good solubility in organic
solvents. PQs are usually synthesized from diamines and bis[2-
this observation in terms of intramolecular interactions, since
there are neither sterically bulky groups nor strong electronic
ones in the molecule. Although not conclusive, the fact that
the molecules form stacks suggests that intermolecular factors
may be signi®cant.
(
alkyl/phenyl)-4H-3,1-benzoxazin-4-one] compounds
Films obtained from PQs based on aromatic diamines have
thermal, dielectric and physico-mechanical properties
comparable with those of common polyimides. It was also
Figure 1
A view of (I) with displacement ellipsoids drawn at the 50% probability
level. H atoms are shown with an arbitrary radius.
2
60 Kovalevsky and Ponomarev ꢀ
H F
8 6
N O
2 4
and C19
H N O
14 2 4
Acta Cryst. (2000). C56, 260±262
18 6
C H F
6 2 4
N O , C19
Kovalevsky
