The behaviour in acid of 4,4-dimethyl-, and 4-dichloromethyl-3,4,5-trimethyl-cyclohexa-2,5-dienones

Tetrahedron

Letters

No.

20,

THE

pp.

1675-1676, 1971.

BEHAVIOUR

IN

ACID

Printed in Great Britain.

Pergamon Press.

OF

4,4-DIMETHYL-,

AND

4-DICHLOROMETHYL-3,4,5-TRIMETHYL-CYCLOHEXA-Z,5-DIENONES K. Chemistry

Department,

L.

Cook

University

of

and

A.

J.

Birminghan-.,

Waring P.O.

Box

363,

Birmingham

(Received in UK 2j March 1971; accepted for publication 1 April 1971) The available kinetic data on dienone-phenol rearrangements ranges

of

dienone

acidity

(I),

and

(1).

We

report

trimethylcyclohexa-2, Dienone

(I)

acid,

HCP04).

Observed

zero

were

(3)

give

HA

(4),

to

(-2. 31 + 0. 10; are

the

gives

Values

just

as

Both must and

be the

shows

of Ref.

fast

and

estimates graph

of

as

for

does show

in the

Ref.

and

5-

4-dichloromethyl-3,4,

5-

sulphuric

the

and

(-2.

follow

bases

10

+ 0. 13)

1.03

for

2 are

correlated

and

Olsen

plots

(0 m-0.

that

log

optical

or

densities

Standard

amide

acidity

close

to

and

for

at

procedures scale

(I)

and

1.0.

These

Olsen’s

or

method

pK’s (5)

(II).

Eqn.

3 shows

m

sulphuric

H2S04

+ 0. 01)

Bunnett

using

Eqn.

52%

and

the

have

values;

aqueous

solutions.

+ 0.03;

amide

in

from

(Table),

acid

dienones

1) (-2.37

(II);

yield

acid

of

Both

kinetics

by

the

28).

straight

Combining

fS/fBHt

changes

lines Eqn.

with

the

of 4

(from

medium

HA.

in Refs. in

for

(I)

with

(I)

isolated

thermodynamic

for

limited

on 4,4-dimethylcyclohexa-2,

first-order

spectra

(Eqn.

Bunnett

theory)

in

(II).

0. 03)

derived

linear

dienones

allowed

the

2

for

(70%

u. v.

r-n values

0.08)

of kl

state

half

and

?

3 and by

transition

(I)

data

pseudo

constants

estimates

(-2.06

with

from

for

1.07

closest

pK

Eqn.

rate

(2)

2TT.

(II).

3,4-dimethylphenol

derived

pK

results

basicity

rearranges,

[B]/[BH+] with

accurate 5-dienone

perchloric

time

supplement

cover

B15

significant pK 2b

2b

studies and

to have

6.

medium and

effects

may

Our

plot

incorrectly

2b. 1675

at

explain of

log

lahelled

some

differences

between

kl

log(water

against

axes,

These

wavelengths,

but

agrees

our

values

activity) with

Eqn.

5

1616

(I)

t

No.20

H+ -<

>

O-Protonated

dienone<

> Transition

[=I+]

LB’] Eqn.

1

loglo

[B]/[BH]+

Eqn.

2

Rate

= kobs

Eqn.

3

-log

Eqn.

4

log

kl kl

= 0. 27 = log

Table

Kinetics

We

t

+ 0.03

3. 33

for

thank

= k,[BH’]

t f /f * BH

ko-log

Product

PK)

-

diaxne]

Ho

->

[$I

= “(HA [Total

state

the

(f

; kl

= kobs(lt[B]/[BH+])

= 0.52

HA t 3.72

= activity

coefficient)

(I)

in aqueous

S.R.C.

for

H2S04

at

financial

+ 0.06

25’C

support

(min

of

this

-1

units)

work.

References 1.

H.

Hemetsberger,

Helv. 2(a)

V.P.

Acta,

Vitullo

(b) 3(a)

Chim.

V. P.

L. P.

and

Hammett,

5.

J.

6.

F.

99,

Grossman,

Chem.

267-278

from J. B.

this

1724

(1968);

G.

Farges

and

A.

S.

Dreiding,

(1966). Tetrahedron

,

Comm.

1970,

Chemistry,

(1970);

(b) A.R.

Eqns.

Letters,

1970,

1559;

688.

Organic

19, 465(1963).

transcribed Yates,

N.

552

‘Physical pp.

Tetrahedron,

K.

49,

Vitullo,

2nd Edition,

4.

Monatsh.,

’

McGraw-Hill,

Katritzky,

56 and 59 in Ref.

A.J.

New Waring

3(a) are

York, and K.

Yates,

incorrectly

paper.

Steven

and A. R. Katritzky,

Bunnett

and F.

C.D.

Johnson,

A.R.

P.

Olsen,

V.P.

Vitullo,

J.Org.Chem.,

Katritzky

Canad. and N. 34,

224

Canad.

J.Chem., Shakir, (1969).

J. Chem. 44,

J. Chem.

1899, Sot.

,’ 42,

1957

1917

(1966);

(B),

1967,

(1964). see 1235.

also