Radiation induced gas phase naphthalene hydroxylation

Chemosphere, Vd.23, No.5, Printed in Great Britain

RADIATION

pp 627-632~ 1991

INDUCED

GAS

PHASE

0045-6535/91 $3.00 + 0.00 Pergamon Press plc

NAPHTHALENE

HYDROXYLATION

Y. K e h e y a n Istituto di C h i m i c a N u c l e a r e del CNR,

C.P.

i0,

00016

Monterotondo

Stazione

( RM ), Italy G. Perez* Istituto ( RM

di

C r o m a t o g r a f i a del CNR, C.P.

10,

00016

Monterotondo Stazione

), Italy

Gaseous n a p h t h a l e n e was s u b m i t t e d to ionizing r a d i a t i o n s in the p r e s e n c e of water, air, and air and water, in o r d e r to study the reactions which lead to the formation of naphthols. In all the e x p e r i m e n t s 2-naphthol was the only s i g n i f i c a n t product c o n f i r m i n g radicalic attack and preferencial a d d i t i o n with respect to h y d r o g e n a b s t r a c t i o n at 55°C. The t e c h n i q u e can be e m p l o y e d to m e a s u r e r e l a t i v e rate constants.

Introduction

Aromatic

hydrocarbons

a t m o s p h e r e s I'2,

and

the

are

extent

important to

constituents

which

they

contribute

smog is of c o n s i d e r a b l e c o n c e r n 3,4. Furthermore, that

the

hydroxyl

c h e m i s t r y 5.

Leighton 6

intermediate data

for

variety have

species

the

obtained

and of

been

( OH

) radical first

such

of

OH

temperature

c o m p o u n d s 7.

carried

activation energy

suggested

in p h o t o c h e m i c a l

reactions room

plays

out

for

an

rate

with

number

( -1.8 kcal Mol -I at 298°C

of OH radicals with naphthalene.

627

OH

urban

photochemical

are

atmospheric could

Subsequently,

be

available

for

dependence and

a

an

kinetic

hydrocarbons

a r o m a t i c s 8,9 ) was

in

radical

temperature

of

to

role

aromatic

constants

Additionally, a

the

air pollution.

radicals

polluted

it is now well e s t a b l i s h e d

important

that

of

a

were wide

studies negative

found for the reactions

628

The

principal

experimental

constants

for r e a c t i o n s

and

photolysis.

be

flash

employed

to

concentration respect

radiolytic

approach

forms

oxygen

of

the

molecule

solutions

involved

in

rate

are d i s c h a r g e

flow

techniques

providing

is

in

can

that

large

excess

the with

to

and

form

the

reactions

to i o n i z i n g

of o x y g e n

in the

formation

of aromatics radiations

established of

oxidation

of f l u o r a n t h e n e - o x y g e n

is

the

polycyclic

that

activated

products.

mixtures

As

a

led to the

f l u o r a n t h e n o l s II

the

by p u l s e

Even

On

in the p r e s e n c e

of isomeric

radiation

relative

C l o u g h I0 s u b m i t t i n g

are

Furthermore, ionizing

species

the o x y d a t i o n

fact the 7 - i r r a d i a t i o n

formation

absolute

decomposition

constants,

reactant

to s t u d y

technique.

hydrocarbons

matter

the

determine

and o r g a n i c s

thermal

rate

to

one.

aromatic of

and

relative

of

used

OH r a d i c a l s

Photolytic

one

the o t h e r

Another

between

obtain

of

techniques

reaction

between

the

leads

to the

naphthalene a

hydroxyl

radiolysis

radical

OH

radical,

addition

adduct,

as

of

generated the

by

radical

observed

in

to

aqueous

t e c h n i q u e s 12.

radiolysis

of

water

v a p o u r 13

OH

radicals

a

systematic

are

formed

at

high yield. the

radiation

basis

of

induced

hydrocarbons

these gas

beginning

results

phase

we

started

hydroxylation

from n a p h t h a l e n e

study

polycyclic

of

as the more v o l a t i l e

on

the

aromatic

compound.

Experimental 0.4 L P y r e x amounts

of

submitted 44°C

ampoules

selected to

60Co

dissolve

the

7-rays

for

the r a d i o l y s i s

chromatograph

filled

with

reported

200

Energy ~L

of

1.6 mg of n a p h t h a l e n e

in Table

ii0 minutes

( Atomic

irradiation

The a n a l y s i s gas

additives

in a 220 G a m m a c e l l After

were

at

i. The

a dose

of C a n a d a methanol

rate

ampoules of

195

and known were kGy

then

h -I

at

). were

added

in

order

to

products.

of the p r o d u c t s equipped

with

was c a r r i e d a

FID

unity,

out on a H e w l e t t - P a c k a r d using

a

i00

m

Petrocol

5890 DH

629

column

(

ID

temperature

=

0.25

from

mm,

film

150 to 250

tickness

0.5

micron

)

the

radiolysis

at

a

programmed

°C.

Results The gaseous

only

significant

naphthalene

confirms

that

hydrogen

abstraction.

the

Table

of

solutions

55°C

naphthalene

affected

Torr

at

product

the

was

The

yield

of

is

2-naphthol, is

of ca.

The

reaction

of

concentration,

radiolysis

2-naphthol.

addition

an u n c e r t a i n t y

i. G a m m a

from

of

absence

the

of

predominant

calculated

reported ' in

Table

binaphthyls with

with i.

various

respect

respect

The

to

data

are

15%.

gaseous

solutions

containing

naphthalene

( 0.5

) Air

N2

H20

(Torr)

(Torr)

(~L)

Run

2-naphthol %

1

-

-

2

760

-

3

760

-

i00

1.7

4

-

760

i00

0.5

The

results

therefore

the

show

that

naphthalene

i00

0.6 0.5

in

all

the

concentration

experiments

the

conversion

can be considered

was

low,

constant.

Discussion It

is

formation

From radicals

well

k n o w n 13

that

the

radiolysis

of O H r a d i c a l s

by reaction

H20

~

the

r e p o r t e d 14

formation

can

water

vapour

OH + H

G-value be

of

for

calculated.

leads

to

the

(i)

reaction

(i),

Comparing

3.7, this

the value,

rate

of

OH

3.27"1011

630

radicals

c m -3

1.77"1010

sec,

with

molecules

It m u s t

the

rate

c m -3 sec,

be considered

of

formation

a loss

that

effect i n t e r f e r e n c e

that

purely

and may be described

first

order

-d[OH]/dt

where

k'

is t h e

first

Furthermore radical

order

at

reactions

be

is 6 . 5 " 1 0 -11

In

order

studied amount

and of

obtained

including

In exceeds

the

Owing nitrogen, transfer yield

its

presence added

run

to

the

loss

is

equation

1011

H20

radicals

c m -3,

+ 0

fact

radical-

(3)

that

the

rate

conditions,

reported

in

does

differ

not

7-radiations

products

to

OH

constant

of

such

run

2.

It

the

can

from

effect

be

the

of

observed

yield

air

was

that

the

of

this

product

oxygen

are

formed,

i.

singlet

molecules

the

above

atmospheric

is

excited-state

hydroxylated

The

r a d i c a l s -I c m 3 sec -I.

formed

under

aromatic

system.

is a s u r f a c e

constant.

-:-b

owing

approach

methanol

fact

i,

(2)

rate

+ OH

result

in r u n

In

of

to

the

from the

= k'[OH]

decay

run

occurs.

v e s s e l s 15 t h e r e

by rate

in

as

c o n s i d e r e d 16,

reaction

Pyrex

OH radicals

concentrations

OH

must

2-naphthol

of O H r a d i c a l s

in c l e a n

removes

of

4 was

of

in

and

of r u n s that

carried

allowing

the

case

air

1 and

it

out.

excited

of O H r a d i c a l s .

of

a non of

radicalic

fluoranthene

oxidation II ,

some

(run

be

result

nitrogen

the

yield

of

2-naphthol

2.

migth

The

3)

to

ascribed shows

the

water,

to

the

absence

that

might

presence

of

of a n y e n e r g y increase

the

•

It is w e l l

known

that

radiolysis,

O(ID)

can

O(ID)

As

water

fact

from

oxygen,

forms

can be expected.

amounts

the

process

I0

activated

+

among play

H20

the

active

a role.

The

species

of o x y g e n

formed

reaction

• 2 OH

(4)

during

531

explain

can

containing The result.

low

oxygen

of

conclusion

as

an

can

to

to

reduce

Owing

to

the

relative

reaction

an

irradiated

the

that

system

substrate

that

Furthermore,

radical

loss

of

and

the

radiolysis

that

final

can

be

reactions

of

hydroxylating

the

radiation and

on

recombination

the t e c h n i q u e

measuring

surprising

observed

hydroxylation

substrate by

was

phase

excess

on

it

a

agents

doses

are

products.

or

remotion

by

can be used to c a l c u l a t e

concentrations

of

products

substrates. the

allows

by

gas

is used,

damages

can not be avoided, rates

the

an

seem

preferentially.

environmental that

could

reactions 17

of n a p h t h a l e n e

radiolytic

fact

by d i f f e r e n t

compounds,

in

product

radicalic

providing

to the organic

surface

radicals

the

underline

study

hydrocarbons

enough

coming

in o t h e r

we

approach

amp o u l e s

OH

among

the ~ p o s i t i o n

In

respect

the

l-naphthol

also

attack

of

and water.

However,

aromatic with

increase

absence

radicals

used

the

method,

the

based

study

of

on

the

the

isolation

relative

of

the

distribution

hydroxylated of

isomeric

Sci.

Technol.,

1109

(1968)

products.

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