Carbonyl fluoride infrared spectrophotometric determination

Journal

of Fluorine

Chemistry,

44 (1989)

261-273

267

Received:November 15,1988;accepted: December29,1988

CARBONYL

A.E.

FLUORIDE

CROCE

and

INFRARED

E.

Instituto

de

(INIFTA),

Facultad

La

Casilla

Plata,

SPECTROPHOTOMETRIC _____

DETERMINATION

CASTELLANO

Investigaciones de de

Fisicoquimicas

Ciencias Correo

Exactas, 16,

Teo'ricas Universidad

Sucursal

4,

y Aplicadas National

(1900)

La

de

Plata,

(Argentina)

SUMMARY

An

infrared

quantitative reactions in

the

the

spectrophotometric

determination between

tration.

range

423-453 The

method

for

presented.

The

383-413

K provide

absorption

K,

gas

cross

and

between

mixtures

sections

fluoride

phase

thermal and

CF2(0F)2

of of

F20

known

CF20

a(1925

cm-l)

=

(4.8*0.3)x10-1'

cm2

molecule

o(1944

cm-')

=

(4.7+O.3)x1O-1g

cm2

molecule

n(1960

cm-')

=

(4.1?0.3)x10-1g

cm2

molecule

were

carbonyl gas

bis(fluoroxy)difluoromethane,

temperature

range

is

and

CO

CO

in

CF.20 concen-1 1944 cm band

at

-1 -1 -1

determined.

INTRODUCTION

Carbonyl tic be

fluoride

studies easily

on

It

is

widely

because

traces

of + H20

such

that

its

water -f it

is

0022-1139/89/$3.50

its

a reaction [l-3].

infrared offers

acknowledged of

as

compounds

by

determination

pulate

CF20

fluorine

identified

quantitative

appears

that

instability

product In most

spectrum deal

CF20

samples

[5].

CF20

of

many

cases,

[4].

a good

in

kine-

CF20

However,

can CF20

difficulty. are

readily

hard

to

reacts

maniwith

[6] CO2

+

2 HF

usually

accompanied

(1) by

variable

quantities

OElsevier Sequoia/PrintedinThe

of

Netherlands

268

co2

unless

I

special

care

is

quantitatively

removed

codistillation

or

ly

concentrations

at

have

low

CF20

determined

ing

this

does

not

fluent used

to

in to

through Other

Unfortunately,

a CF2O/CO2

filtration

CF20

pass

gas.

from

by

substance

taken.

at

CO2

and

HF

the

column

CF20

in

the

by

by

on

and

CO2

is

columns presence

gel

co-workers

measured

The

in have

fluorine

[9]

convert-

column.

[10,11]

of

be

particular-

quantitatively

a silica

and

cannot

fractional

temperatures,

Heicklen

mixtures

chromatographic

determine

mixture

low

[7,8].

gas

CO2

the

HF ef-

been

containing

compounds. On in

the

other

a number

analytical

of

hand,

CF20

chemical

methods

have

actual

CF20

concentration

Matula

[15]

have

the

The

fluoride

ion

and

co-workers

10)

of

CF20

of

at

ther

the

slit

were

indicated,

can

also

5.10

P

width

though

in

be

for

CF20

and

followed

out.

by

However, [16].

absorption

the

the and

technique both

carried

0.013

CO2

several

establish

unsatisfactory

the

Heicklen

coefficient(base but

Torr-'cm-l,

measurements

presumably

with

Drennan

mixtures,

also

are

the

to

of

CF20/C02

reported an -1 (1960 cm ) of

used

order mixture.

chromatographic

fluoride

have

in

a CF20/C02

together Therefore,

determination

determination for

even

[12-141.

a gas

hydrolysis

methods

produced

proposed

in

quantitative

alkaline

volumetric

been

described

simultaneous

co2.

is

reactions

nor

the

temperature

nei-

temperature

was

near

296

K

[171. In

the

reaction in

the

course

and

CO2

the

amount

ed.

Because

CF20

by

cross

gas

range

system

has

CO2

mixtures F20

is

the

gas

K,

the

present

this

it was

clearly

thermal

at

can 1944

species

[18].

been

CO

Besides,

be easily -1 cm band

[19,201,

has

and

established

products

reaction

frequency

phase

CF2(0F)2.

determin, is

CF20

not

absorp-

determined

from

plot. phase

temperature

that

of

reaction

absorption

other at

only in

infrared the

This

sults

study

383-413 the

formed

section

a Lambert-Beer The

were

CF20

interferred

kinetic

range

CF20

of

the

bis(fluoroxy)difluoromethane,

temperature

that

tion

of

between

of

thermal

reaction

423-453

K

proved

to

exactly

commercially

employing

this

be

known

[13]

F20

constitutes

a reliable

method

concentration,

available

reaction

between

as

and CF20

easily source

and

CO

another to with

CF

obtain the

purified. are

in

also

2

the 0 source. CF20/

advantage The

re-

presented.

269

EXPERIMENTAL

Gas mixtures conventional been

described

outer

was

[18]. A quartz

reaction

than

regulator.

connection

with

The reaction

spiral

the vessel,

vessel

manometer

a mercury

trap

to better

used

manometer.

which

was

to a standard

also

in a

which

vessel,

aluminium

?O.l"C

has 45 mm

was

isolat-

block.

by a Lauda

connected

as a null

The furnace

The R-10

to a

instrument could

connected

vacuum

prepared

in a thermally

controlled

quartz

spiral

studies,

heated

electronic

up and down

were

in kinetic

from an electrically

Bodenstein

volume

concentration

used

and 100 mm long, was housed

made

temperature

CF20

system

elsewhere

diameter

ed furnace

of known

static

through

line used

in

be moved a low

for gas hand-

ling. Bis(fluoroxy)difluoromethane Cauble

and Cady

liquid

oxygen

rature

and kept

Oxygen

cooled

with

from Matheson

light.

distilled liquid

at low tempe-

(USA),

as a gas in a Pyrex it was

of

[22] at the

air.

Gas Products

stored

Periodically

by the method

by filtration

trap-to-trap

in a trap

at 77 K was kept

from

was prepared

was purified

temperature,

difluoride

ly degassed protected

[21]. It

condensed

previousflask

at 77 K and

degassed. Carbon high

monoxide

purity

through

99.9%

nitrogen

a trap

cooled

The infrared

from Matheson

from La Oxigena

at 153 K and stored

spectra

were

recorded

spectrophotometer.

A 10 cm long

meter,

NaCl windows,

fitted

photometric Special reaction

RESULTS

with

Gas Products

(Buenos

in Pyrex

in a Perkin

(1) Pyrex was

Aires)

cell,

employed

(USA) and were

passed

flasks. Elmer

325

30 mm outer

in the spectro-

determinations. care was

vessel

taken

to avoid moisture

and infrared

in the vacuum

line,

cell.

AND DISCUSSION

The reaction

[18] occurs

without

variation

in the total

ber of moles CF2(OF)2

dia-

+ 2 CO

+

2 CF20 + CO2

An = 0

(2)

num-

and

follows

100 at

Torr 403

the

of

K.

pressure

and

the

ved

(within

and

of

difference

was

kept with

the

equilibrated

tion

measurement

sures In CO

The

up

at

with

to

+

The

amount

+

of

sure

change were

above

for

sidue

at

K.

cell

was

out.

by

vessel

two

three

pressure

or

appropriate

were

of

pres-

infrared

absorp-

repeated

to

mixtures

the

were

as

the

concentration

measurements

of

calculated

reaction

the

diluting

obser

amount

the

operations

Low

403K

was

the

be

off.

at

and

an

and

These

obtained

can

trap

pumped

change (Z),

flushed

mixture,

temperature

spiral

CO

pressure

this,

react

measured

equation

pressure

After

range.

of

in

the

CF20

+

CF20

at

as

original

carried

(be-

with

out

at

in

(2).

and

pres-

to

and

occurs

(3)

(3)

way

in

an

reaction

F20

[13]

equals

the

temperature.

a similar

However,

corresponds

This moles

between

= -1

reaction

volume

out

of

An

by

reaction

source.

number

CO2

constant

the

CF20

total

formed

reaction K

experiments,

employed

carried

77

initial

then

This

to

consumption)

and

unreacted

was no

to

infrared

this

were

series

2 CO

until

CO

Torr.

K was

ments

the

absorption

a decrease

F20

mixture

experiment,

allowed 30%

vessel

the

consumption.

77

carried

60

other 423

CO

pressure

CF20)

nitrogen.

CO

at

at

whole

1 Torr

reaction and

CF2(0F)2/CF20/C02

sure

the

(s

of

According

the

K,

were

the

repeated

between

298

CO

40 minutes

baths

condensed

fraction

at

a typical

Torr

down,

Torr).

equals

volatile

low

the

20.2

the

100

oxygen

distillation

the

cover

moved

In

kinetics.

approximately

liquid

formed

times

CF2(0F)2

was

into

The

CF20

order

After

furnace

placed

a second

as

this

These

the

one

case,

equimolar

total

experi-

described

the

mixture

pres-

condensed of

CF20

itself,

the

reand

co2.

1925-1944-1960

As

for

spectrophotometric -1 cm band [8] was

the

until

slit

the

width

the

was recorded at the fixed -1 -1 cm , at 1925 cm and at -1 oflcm . The absorption spectra 4-60

were

Torr.

found This

band

to

be

band

measurement firstly

was

resolved.

frequency 1960 cross

cm

of -1

obeys

of the

while

Then,

the

with

sections

independent

therefore

scanned

band

the

derived pressure

absorbance

center,

a spectral

in

Lambert-Beer

1944

slit

from

whole

reducing

width

these

the

range

law

over

271 0.8

0.6

0

1

2

Pressure 1. Plot

Fig.

CF20

TABLE

of

3

4

5

of CF20 (Torr)

absorbance

source:

at

0 reaction

1944

cm -1

(2),

against

CF20

0 reaction

(3).

pressure.

1

CF20 absorbance at 1925. 1944 and 1960 cm-' (T = 298 K. 1 = 10 cm)

[CF20]/Torr

A

1925

cm

-1

A

1944

cm

-1

A

1960

0.5

0.086

0.076

0.073

0.6

0.10

0.10

0.092

0.9

0.15

0.14

0.12

1.0

0.17

0.16

0.14

1.2

0.20

0.20

0.17

1.4

0.20

0.20

0.18

1.5

0.26

0.24

0.22

1.9

0.28

0.27

0.23 0.32

2.3

0.37

0.36

2.4

0.39

0.38

0.34

4.3

0.68

0.68

0.59

4.4

0.69

0.67

0.59

cm

-1

272 the

range

tion

and

which

of

the

and

function

of and

at

absorber CF

absorber This

used.

absorbance

sorbance ing

pressures

temperature

the

2 cross

absorption

center

amount.

0 pressure

amounts

is

Table data.

sections

plotted

band

1 shows

the

these

CF20

at

cm2

molecule

c(1944

cm-l)

=

(4.7+0.3)x10-19

cm2

molecule

o(1960

cm-l)

=

(4.1+0.3)xlo-~~

cm2

molecule

ment

with

tained

represent

absorption the

from

cross

previously

measurements

three

value

reported

value

performed

at

K

can

in as

a

set

of

the

follow-

be

ab-

calculated

-1 -1 -1

standard

section

whole

results, 298

(4.8&0.3)x10-1'

estimates

1

is

the

=

error -1 cm

resolu-

of

cm-l)

1960

the Fig.

From

for

at in

o(l925

The

and

illustrated

deviations.

is

in

[17]

which

total

The

excellent

agree-

has

pressures

been of

ob-

up

to

1 atm.

ACKNOWLEDGMENTS

This CIC in

de

research la

the

present

between

the

sity

La

of

project

Provincia

wagenwerk

de

work

was

University Plats

for

is

supported

Buenos

provided of

by

Aires. by

Mainz

a partnership

the

of

also

project

CONICET the

and

thank

with

the used

Agreement

the the

and

equipment

Cooperation

(F.R.G.) We

(Argentina).

the

Part

UniverStiftung

Professor

J.

Volks-

Troe.

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