Studies on Enzyme Action. 313 
It will be seen that the two radicles H and OCHs shown as attached to 
the one carbon atom merely occupy different or reversed positions relatively 
to the two other radicles with which the carbon atom is connected. 
As to the manner in which the hydrolytic attack takes place, two views 
are possible: the one being that the compound behaves much as the simple 
ether CH3.0.CH; would and that the hydrolyst becomes associated with the 
oxygen atom to which the CHs group is attached; the other being that the 
attachment is to the oxygen atom in the ring. On the former view, it is to 
be supposed that the two isomeric compounds wouid be hydrolysed with 
equal readiness, as the CH;0 groups are equally weighted; but on the latter, 
it is conceivable that the methoxy-group is less easily accessible to hydro- 
lysis in the one case than it is in the other; or it may be that an inductive 
effect is exercised by the one oxygen atom upon the other which renders the 
oxygen atom in the ring either more or less attractive of the hydrolyst, as the 
case may be. 
In the galactosides, the CH30 group occupy the same relative positions as in 
the two glucosides ; but the contiguous oxygen atom in the pentaphane ring 
must be supposed to occupy a position slightly different from that which it 
occupies in glucose, its connection with the carbon atom on the right being 
slightly different, as shown in the two following formule :— 
Hom , 
oo SY Pe 
CH,0.C.H BH.C—C—C.OH. CH;0.C.H CC Or 
4 VO 1 Xe / A OHH 
Aa WA 
a-Methylglucoside a-Methylgalactoside 
Apparently, seeing that the galactosides are the more easily hydrolysed, 
this difference is sufficient to render the hydrolyst—the attack of which in 
all probability is directed from the oxygen atom in the ring—more accessible 
to the neighbouring CH3;0 group than it is in the glucosides. The behaviour 
of the glucosidic acetates appears to be in accordance with such an interpre- 
tation.* In models of glucose and galactose constructed with tetrahedra to 
represent the carbon atoms, if these atoms are arranged in a vertical plane the 
oxygen atom in the ring occupies somewhat different positions more or less 
outside this plane ; the difference in the relative positions of the OCH; group 
and the oxygen atom in the ring, according as the position of these on either 
side of the ring plane is varied, then becomes apparent. 
* Of. Armstrong, E. F., and Arup, ‘Chem. Soc. Trans.,’ 1904, vol. 85, p. 1043. 
2B 2 
