114 REPORTS ON THE STATE OF SCIENCE. 
constitutional formule should be assigned from the results of single rea¢- 
tions, as has been done by Perkin and Pickles ' in the case of the tetra- 
hydroisophthalic acids. Abati and Minerva” have isolated hydrophthalic 
acids by the reduction of phthalic acid with sodium amalgam, and give 
the principal properties of these acids and their anhydrides. 
Steric Hindrance in the Formation of Rings.—The interaction of the 
1 : 4-dibromides and primary aromatic amines has been previously shown 
by Scholtz * to take place in one or two ways, according as to whether the 
primary amine contains a substituting group in the ortho position or not. 
Thus with o-xylylene dibromide and aniline or m- and p toluidine a five- 
ring compound, is formed :— 
OH,Br FN 
C,H, +H.N.CH, = CHX ">N.OH, + 2HBr, 
Ncu,Br CH,“ 
whereas when o-toluidine is used an open chain substance results :— 
CH,.NH.C,H,.CH, 
2 
OHS + 9H,N.C,H,.CH,. = C,H 
\cuH,Br 
K + 2HBr. 
CH,.NH.C,H,.CH, 
The reaction has now been extended to the formation of six-ring 
systems, where the condensation of numerous substances has shown 
that exactly similar conditions hold good: for o-toluidine condenses 
with pentamethylene dibromide to give pentamethylene-di-o-toluidine, 
(CH,);.(NH.C,H,.CH;)., whereas with m- or p-toluidine there is formed 
m- or p-tolylpiperidine. 
Optical Influence of Conjugated Unsaturated Groups.—Kay and 
Perkin ® have shown that the magnetic rotation of d-limonene differs 
from that of A®*-p-menthadiene, of which the value is abnormally high, 
and they expressed the belief that this was due to the presence of two 
conjugated double bonds. Bruhl® points out that this is correct, and 
that the high value could have been predicted with certainty, for Bruhl’s 
previous work has proved that the numbers for the magnetic rotations 
and refractive values of substances are always largely increased by the 
presence of conjugated double linkings, not only C: C.C: C but also 
C:C.C:0O. Only benzene derivatives, which contain monovalent atoms 
or groups substituting hydrogen atoms of the ring, give normal values, 
and here it is presumed that the three double bonds mutually neutralise 
one another. As soon as the symmetry of the six carbon atoms is 
disturbed by the introduction of CH, between the members of the ring, 
or by coupling the ring with other unsaturated groups, such as C : C, 
C: 0, NO,, &c., then the characteristic increase in value due to the con- 
jugated bonds is shown. 
Velocity of Chemical Change in the Polymethylene Series.—The follow- 
ing may be quoted as some of the more important general results of the 
1 J.0.8,, 1905, 87, 293. 2 Cent. Blatt., 1907, 1, 887. 
8 Ber., 1898, 81, 414, 627, 1154, 1707; and 1899, 32, 848. 
4 Scholtz, Ber., 1907, 40, 852. 5 J.C.8., 1906, 89, 839. 
8 J.C.S., 1907, 91, 115. See also Ber., 1907, 40, 878. 
