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S.

YANARI

687

centration

of hydrindantin

as factors

primarily

responsible

for the differ-

ences in reaction rates The increase in the

and color

yields.

reactivity

of these

diastereoisomers

with

increasing

concentrations be inversely

of organic solvent related to the dielectric

suggested constant

that the reaction of the reaction

rates mixture.

might hc-

cordingly,

1,4-dioxane,

as

the

organic

solvent

.

which The

has data

a dipole moment of

with

dioxane

were

zero, not

was substituted

significantly

dif-

ferent from

those

in Fig. 3.

Diflerences

in

Theoretical

Color Yields from

Peptides-The

unexpectedly

L-Leu-L-Tyr

(Fig. 1)

previous

experiments

high

“molar”

color yield

from

ther,

since it

was evident

from

was

investigated

that

impurities

fur- were

FIG. contained total volume, 4. Maximal 1.0 ml. I .2 ml.

molar color yields of hydrindantin-ninhydrin

from

dipeptides. reagent

and

reaction

mixture

pmole

of

dipeptide;

Each

0.08

not responsible

for this result.

Each alanyl

and leucyl

dipeptide

tested

gave values well as with

approaching

27 with

the

SnC&-ninhydrin

the hydrindantin-ninhydrin

reagent

reagent.

At

high

concentrations

as of

methyl

Cellosolve,

the rates of reaction

of dipeptides

were increased

to the

extent that to those of L-Leu-Gly,

even n-Leu-n-Tyr

yielded a value of 1.7 (Fig.

the leucyl nn-Ala-Gly,

peptides in Fig. and L-Leu-n-Tyr.

4 were

obtained

4). with

Data similar n-Ala-L-Leu,

On

the

other

hand,

entirely

different

results

were

obtained

from glycyl

dipeptides.

The kinetics

of the color development

from Gly-Gly

and Gly-

L-Tyr (Fig. complete in

4) were less than

similar to those of amino 15 minutes, yielding molar

acids. values

The reactions

of

exactly

1

.

were Sim-

ilar reaction

kinetics

were exhibited

by Gly-L-Leu

and L-Ser-L-Tyr.

for

7 Molar L-Ala-L-Ala

color

yields

(30 minute

and

L-Ala-L-Ser

reaction by Dowmont

period) and

of 1.5

to 1.6

Fruton

(7).

have

been

reported

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