Polyfluoro-1,2-epoxy alkanes and cycloalkanes. Part IV [1]. Thermal reactions of the epoxides of the pentamer and hexamer oligomers of tetrafluoroethene

of Fluorine Chemistry, 27 (1985) 7 l-84

Journal

Received:May23,1984;

accepted:June22,1984

POLYFLUORO-1,2-EPOXY THERMAL

REACTIONS

OLIGOMERS

71

ALKANES

AND CYCLOALKANES.

OF THE EPOXIDES

PART IV [I].

OF THE PENTAMER

AND HEXAMER

OF TETRAFLUOROETHENE

P.L. COE*, A. SELLARS, J.C. TATLOW

Chemistry

Department,

Birmingham

B15

2TT

University

H.C. FIELDING

and G. WHITTAKER

ICI

Division,

PLC,

Mond

of Birmingham,

P.O. Box 363,

(U.K.)

The

Heath,

Runcorn,

Cheshire

(U.K.)

SUMMARY

Oxirans hexamer 300-500' Thus,

(1) and (Z), derived

oligomers

respectively

of tetrafluoroethene,

alone and in the presence

oxiran

(l), pyrolysed

ene (TFE tetramer)

of cyclohexene,

alone, afforded

perfluoro-2,3-dimethylpent-2-ene (5a, 5b).

from the pentamer

were pyrolysed

and

over Pyrex glass at

bromine

and toluene.

perfluoro-2-methylbut-1-ene

(3),

(4) and (E) and (Z) perfluoro-2,3-hex-3Co-pyrolysis

of (1) with bromine

afforded

(E)

and (Z) 2-bromoperfluoro-3-methylpent-2-ene

(6a, 6b), whilst with toluene,

(E) and (Z) 2H-perfluoro-3-methylpent-2-ene

(7a, 7b) were obtained:

with excess

cyclohexene

alone, gave only (3). mixture

also gave (7a, 7b).

In the

presence

The oxiran

of bromine,

of 1-bromoperfluoro-3-methylpentan-2-one

methylpentane

(9).

Co-pyrolysis

perfluoro-3-methylpentane

(10).

(2), on pyrolysis

(2) gave an equimolar

(8) and 3-bromoperfluoro-3-

of (2) with toluene yielded Pyrolysis

(l-methylpropyl)lketne

0022-1139/85/$3.30

(3) and 3H-

of (2) with cyclohexene

gave perfluoro-3-methyl-2-(l-methylpropyl)pent-2-en-l-oylfluoride pentafluoroethylcyclohexane

(1)

at 175' (ll),

(12) and perfluoro[(l-ethyl-1-methylpropyl)

(13).

0 Elsevier Sequoia/Printed

in The Netherlands

72

INTRODUCTION

As part of our study [2] of the reactions gomers,

we have recently

epoxides

obtained

reported

[I] the preparation

by the direct reaction

alkenes with sodium hypochlorite. hexafluoropropene difluorocarbene related

its fairly

low boiling

high boiling,

considerable

reported

of

perfluoroperfluorooxiran,

used as a source of

[3], its chemistry

[4].

oli-

A disadvantage

and that of

of (HFPO) is

(-27') so that it is not easy to store and

handleable

from TFE pentamer liquids

(1) and hexamer

and in principle

(2) are

might be good

and CF2: respectively. by consideration

and hexamer

steric

as the products %-

point

is supported

both the pentamer

decomposition

the oxirans

easily

of CF3CF:

This

The most widely

have been reviewed

In contrast

of a number

of the corresponding

(HFPO), has been extensively

by thermal

compounds

handle.

sources

oxide

of tetrafluoroethene

crowding

derivatives

would

of the two compounds,

be expected

due to the bulky perfluoroalkyl

from loss of CF3CF:

CF3 andsg-<

of models

should be much

and CF2:, respectively,

to have groups, wherethe ketones

less strained.

B

RESULTS

We have examined

the thermal

over a wide range of temperatures glass pieces

as column packing

study of the thermolysis fluorinated

bromine

Oxiran

as radical

at 180-200°C,

near to 300'.

of a mixture

of the oligomers

(1) and (2)

method with Pyrex previously

themselves

in our

and their

[5].

sources,

(1) was significantly

latter decomposes pyrolysis

using a flow pyrolysis

the oxirans were pyrolysed

and toluene

of the oxirans

similar to that described

reactions

derivatives

Firstly

stabilities

alone, and then in the presence and cyclohexene

more stable to heat than is HFPO, the but (1) only decomposed

At this temperature

containing

three major products

significantly

(1) afforded

and five very minor

components.

components

in almost equal amounts. They were easily identified (by a 19 of the i.r. and F n.m.r. spectra with those of authentic

as perfluoro-2-methylbut-1-ene

afforded

yield

of the mixture

samples)

by gas chromatography

on

a reasonable

Separation

comparison

trifluoromethylcarbene

1).

No products

were

the three major

(3), perfluoro-2,3-dimethylpent-2-

ene (4) and (E) and (Z) perfluoro-2,3-dimethylhex-3-ene (5a, 5b) (see Scheme

of

as a carbene trap.

attributable

identified,

(TFE tetramer)

to the elimination

but trifluoroethanoylfluoride

of was

73 present

(i.r. spectrum).

of fluorocarbons with bromine bromine

(including

or toluene

or hydrogen

with the rupture at 300-350'.

[61 we have shown that co-pyrolysis

oligomers

of TFE and their fluorine

distinguishes

appearing

the pathways

in the products

of the weakest

bond.

the presence

elemental

analysis

of one bromine

characteristic

of thermal

at positions

Oxiran

Only one product was formed

by I9 F n.m.r.,

empirical

Previously

[5])

corresponding

(1) was pyrolysed

in good yield.

with bromine

This was identified

and mass spectrometry.

atom, indicated

adducts

decomposition,

The latter showed

by the molecular

ion as the

doublet

formula

at 260 and 262 mass units, corresponding to an 19 F n.m.r. spectrum confirmed the of C6BrFII. The

c2F5, of the CF3 - C-group and showed two groups of peaks in the / c2F5 These data are consistent with the compound being (E) and (Z)-

disappearance

ratio 55145.

2-bromoperfluoro-3-methylpent-2-ene

(6a, 6b).

Co-pyrolysis

of oxiran

(1)

with toluene afforded a mixture of two major components in equal proportions. 19 F and IH n.m.r. spectroscopy indicated the product was a mixture of closely

related

compounds

probably

showed the loss of the characteristic

groups,

bond, there was also a single

CF2 group.

a quartet with further

corresponded a mixture 7b). g.1.c.

to a formula

The 'H spectrum

showed

Elemental

small coupling.

of C6HFII.

again

c2F5, CF - C-group and indicated the pres3/ c2F5 two of which were attached to a double

ence of three trifluoromethyl

resonance,

The lg F spectrum

E and Z isomers.

These data suggest

a single

analysis

the product

of the E and Z isomers of 2H-perfluoro-3-methylpent-2-ene

to be (7a,

It was found possible to separate the isomers on semi-preparative 19 F spectra of the individual isomers were measured and, on the The

basis of the chemical

shift differences,

it was possible

to assign structures

for each isomer. A similar cyclohexene, corresponding

result was obtained

compounds

Scheme

of release

of the carbene

of strain

(2) should be a good precursor

compound

No decomposition

as outlined

with Nothing

was detected

above suggested

under a variety

that

Accordingly of conditions

(see

seemed to occur below 175' but at this temper-

ature and above, the oxiran readily attributable

products.

intermediate

of difluorocarbene.

(2) was heated with cyclohexene

2).

(1) was co-pyrolysed

(7a, 7b) being the only isolable

to the direct trapping

The postulation oxiran

when oxiran

to difluorocarbene

decomposed.

formation

However,

no products

could be detected.

It is known

74 from previous

work [3] with HFPO and cyclohexene

difluoronorcarane, this experiment

and obtained

difluorocarbene

extrusion

oxiran

similar

results.

adduct, we repeated

Thus, we conclude

is not a significant

When the latter and cyclohexene

(2).

that the carbene

is stable at 180' and to test our methodology

decomposition

that

pathway

were heated together

sealed tube at 175' for 24 hr, three products

resulted,

for

in a

which were separated

The first product isolated was a liquid with strong bands in its -1 at 1860 cm indicative of the presence of an acid fluoride -1 19 and at 1620 cm suggesting a C=C bond. F n.m.r. spectroscopy again

by g.1.c.

i.r. spectrum

indicated

gration

the absence

pattern

CF3 groups

suggested

c2F5 the presence

indicated,

an empirical

chemical

in a mixture

nent was readily

formula

identified

of C10F180, which corresponds

formed;

ketene

(2) was pyrolysed

compound,

readily

(2) in the presence

yield,

in approximately

afforded unknown

equal

which

Other peaks

in structural

amounts.

determination.

fluorine

Separation

to C6BrF100

amine afforded

Thermolysis

spectrum

atom. These data suggest

by preparative

of oxiran

g.1.c.

(9) and a previously at m/e 357 and

(8).

showed a strong band at

showed C2F5, CF3 and CF2Br and the product Reaction

N,N-dimethylbromodifluoroethanamide,

3H-perfluoro-3-methylpentane

of the

in fairly good

and C6F110 respectively.

'The i.r. spectrum

the structure

(3), was

and m/e 129 and 131 (CF2Br)+ were useful

trifluoromethylheptafluoropentan-2-one

thus supporting

Pyrolysis

gave two products

showed peaks in its mass spectrum

1780 cm-l (C=O) and the lg F n.m.r. a tertiary

(12) and the

as perfluoro-2-methylbut-1-ene

could be detected.

at m/e 247 (M-CF2Br)+

to perfluoro-3-

The second compo-

in the flow system at 330' a single non-

of bromine

359 and at m/e 297 corresponding

products.

(11).

the known 3-bromoperfluoro-3-methylpentane compound

atom, two

(13).

identified

no other major product

oxiran

fluorine

of E and Z isomers.

as pentafluoroethylcyclohexane

as 'hexamer'

When oxiran gaseous

and the inte-

from the highest mass peak and the breakdown

methyl-2-(l-methylpropyl)-pent-2-en-l-oylfluoride

third component

shifts

of one tertiary

and two CF2 groups contained

Mass spectrometry pattern,

c2F5 of the CF3 >-group;

to be 1-bromo-3-

of (8) with dimethyl-

via a haloform -

cleavage,

(8).

(2) in the presence

of toluene

(10) and no significant

afforded

(3) and

oxygen containing

‘75 CF I3 c-c 101

cF3

/ \

C2F5,

&

F

c=c=

+

CF' 3

3

CF ' 3

(7a, 7b) Scheme

CF

c2F5, C=CF2

+

CzF5, cF / 3

CF3

,c2F5 c=c\cF 3

(6a, 6b)

1

In all schemes:

c2F5 \ CF3 - C 5 / c2F5

C2F5 F\-\C: CF ' 3

DISCUSSION

From these results of the carbenes decompositions radicals

it is clear that there is little,

:CF2 or :CFCF3 in these pyrolytic seem to be controlled

formed

by rupture

sition of these radicals consider

first the oxiran

(l), assuming

c2F5 CF3 c2F5

h-c-I, /

bonds, but the further

b .

CF 13 - F

of decomposition

(A)

and

c2F5 CF3;,'C c2F5

carbenes.

C-O bond cleavages

with this, then the two diradicals CF I3

The

stabilities

do not give these particular

step, and most of the products conformity

by the relative

of the weakest

if any, formation

reactions.

would which

CF F 131 - < - S - CF3

.

of the decompoIf we

as the first

appear to be in

can form:

(6)

76

A330’C A330°, A330°, A175’,

(i)

(ii) (iii) (iv)

Br to?uene cyclohexene

CF,Br

(8)

c2F5

\ /

C=CF2

(3)

+

I

H

(14)

(10)

CF3

L>= -c c

//

CF

0 Scheme

]- C t b

-(- + C6HllC2F5 (13)

2

A

(1)

(11)

-

-----C-f-F 1.

(ii)

CF CF 1313 0. (B)

c2F5 'c=c CF ' 3

Scheme

3

AR 'CF

3

(12)

c2F5

(10)

(3) (i) (ii) (iii)

Scheme

(8)

(9)

loss of CF3 toluene Br 2 4

(F)

(ii) J

c2F5 lczc CF ' 3

x +c s 'COF

(11) (i) (ii)

Scheme

loss of Fe loss of C2F5'

5

F-

(13)

78 From our previous radicals

are favoured,

work

[5,6] showing that the most heavily

a conclusion

(B) seems the more

likely.

outlined

3, though

in Scheme

CF3COF to give carbene account

C.

B now has two possible additions

Additions

for most of the products

methylbut-l-ene

pyrolysis

(3).

c2F5 CF3 &m(D) /

the radical

by others

modes of reaction

to carbene

as

C by species present

The exception

has appeared

is perfluoro-Z-

previously

CzF5, the CF3 ;C-group,

containing

substituted

[7], diradical

to it seem less likely than loss of

found.

This product

of a product

also supported

[5] in the

and clearly

c2F5 by loss of CF3. The cleavage

comes from

of the central

bond

c2F5' c2F5, , of type CF3/C - C\ is a facile process [5]. In the present ,.,L2'5 case, cleavage in the oxiran (1) of this type of bond to give two radicals in a species

competes

to some extent with C-O cleavage

the radical

(D) could arise from breakdown

Rupture

of oxiran

when the isolated

a cleavage

This

(10) (Scheme 4).

products

suggests

decomposition

alone, or in the presence

can all be accounted (0) which

of

for in terms of

can respectively results

give (3) and

[5] and

confirms

of this decomposition

more ready extraction/formation of both intermediates

of bromine

At lower temperatures

(1) was recovered

amounts.

in a static reaction

However,

from a different

pathway.

allowed the direct

(175-180')

unchanged

with cyclohexene,

of bromo-

in the presence

in virtually

Compound

However,

it is suggested

of the alternative

breakdown

of the oxiran ring as shown in Scheme

of

quantitative

oxiran

(12), the minor product,

of C6H10 with some C2F5. formed

as above.

the involvement

Here, the

(2) gave

((ll), (12), (13) Scheme 2) and (11) and (13) clearly

arises from reaction the molecule

radicals

formed

in the presence

pathway.

D and E leading to the isolation

cyclohexene,oxiran

three products

(3) and (10)

of the other radical

In fact, only the pyrolysis

the reality

(8) and (9).

The fact that only products

[8].

deep seated breakdown

(E) to give small fragments. of bromine

compounds

Alternately,

some of our recent work [9] with perfluoro[(l-ethyl-l-methylpropyl

isolated

trapping

(B).

is in keeping with previous

(1-methylpropyl)]ethanolide were

of diradical

(2), either

to give the same radical

parallels

ring.

of bonds of this type must occur in the thermal

at higher temperatures toluene,

of the oxiran

arise

presumably

in the breakdown

of

that (11) and (13) require

of (2), i.e. C-O bond cleavage

5 to give diradical

F.

This

79

breakdown

pattern

could have given rise to difluorocarbene.

other C-O bond breaks to give diradical the acyl fluoride

radical

form the acid fluoride fluorine

Although to simple

of the ketene

stability

these thermal

fluorocarbenes,

inertness

steric crowding results

[l].

decompositions

by loss of Fe to give loss of C2F5. to loss of the "acyl"

This again demonstrates

did not give the desired

they have nonetheless high thermal

This stability

at one of the carbons

on the thermal

(13).

the

of bisperfluoroalkylketenes.

(1) has a relatively

chemical

F followed

There then occurs either

(11) or rather more surprisingly

and the formation

the high thermal

Oxiran

G.

However,

stability

proved

stability

interesting.

in keeping with its high

is markedly

in oxiran

route

lowered with

increased

(2) in keeping with earlier

of fluorocarbon

derivatives.

EXPERIMENTAL

The pyrolysis

Apparatus

tube was constructed

of Pyrex glass

(75 cm x 1.5 cm) packed with small pieces of Pyrex glass tube 1 cm long x 0.4 n-m) mounted elements

wound

chromatography preparative

was carried

out using a Pye 104 series machine

using the columns

epoxide)

The contents

carbon dioxide

tetrafluoride examined major sample

(1)

tube at 305-31O'C

the volatile

fire

Gas

with a semi-

specified.

of perfluoro-2,3-dimethyl-2-(l'-ethyl-l'-methylpropyl)

(5 dm3 h -' ), the products air.

of electric

in fire bricks for 50 cm of its length.

(pentamer

pyrolysis

and heated by means

in channels

attachment

Pyrolysis oxiran

vertically

(3.

The oxiran

(112.5 g) was introduced

being collected

in a glass trap cooled

of the trap were slowly warmed

by i.r. spectroscopy

by analytical

gas chromatography

and five very minor

components.

(2.5 g) of the mixture

The residue

N2, 1 dm3 h-l) gave (i) a mixture

of silicon-

and was shown to contain

three

separation

Chromasorb

of four very volatile

of

(57.4 g) was

Gas chromatographic

(Diisodecylphthalate

in solid

Examination

showed the presence

and trifluoroethanoylfluoride.

in liquid

via a trap cooled

then ice salt (-15') to room temperature.

materials

into the

over 5.5 hr in a stream of dry nitrogen

of a

P (1:3, 45',

components

(0.3 g)

not identified; by comparison sample

(ii) perfluoro-2-methylbut-1-ene (3) (0.42 g) identified 19 F n.m.r. spectra with those of an authentic of i.r. and

[5]; (iii) perfluoro-2,3-dimethylpent-2-ene

identified spectrometry

by comparison

of i.r. and "F

n.m.r.

(m/e 331 (M-F), m/e 281 (M-CF3),

(4) (0.5 g), b.p. 71-72' spectra

[2]

231 (M-C2F5).

and by mass C7F14 requires

80 M 350);

(iv) E and Z perfluoro-2,3_dimethylhexene

(0.6 g) identified

Co-pyrolysis

by comparison

with

in a stream

of nitrogen

were collected material treated

(2 dm3 h-l) over a period

the excess

bromine

and washed distilled revealed

with water

(100 cm3).

the fluorocarbon

The residue

the presence

of one major

Purification

(Peg A/Chromasorb

of a sample

Co-pyrolysis

couplings

6 hr.

The product

excess

of toluene

C6BrFll

The lg F n.m.r.

of minor

g.1.c.

at 35O'C

The epoxide

Separation

(DinosylphatelChromasorb

retention

g.1.c. to contain of a portion

F n.m.r.

spectrum

two components

as

them)

in equal

(1.12 g) by semi-preparative

g.1.c.

P 1.10, 55', N2, 1.8 dm3 h-l) gave (i) Z-2H-

perfluoro-3-methylpent-2-ene

(7a) nc (0.36 g), b.p. 42'C (Found m/e 263 C6FllH requires

M 282; (ii) E-2H-

(7b) nc (0.34 g), b.p. 52'C (Found m/e 263 (M-F

Elemental

analysis

C6HF11 requires

on a mixture

of (7a) and (7b)

C, 25.5; H, 0.3%.

Co-pyrolysis

of (1) with cyclohexene

above the oxiran

(25.8 g) and cyclohexene

in the same proportions.

(the large

aby;t 15% (ca_ 5-6 g) of

time and

(M-F), m/e 213 (M-CF~), m/e 163 (M-C~F~).

M 282).

(2 dm3 h-l) over

from the toluene

layer and no attempt was made to separate

perfluoro-3-methylpent-2-ene

gave: C, 25.8; H, 0.5.

(25.8 g) and toluene

in a stream of nitrogen

was shown by g.1.c. to contain

with the same g.1.c.

was shown by analytical

C, 19.9;

showed two groups

to the E and Z isomers distinguish-

(10.7 g), after separation

in the fluorocarbon

requires

spectrum

(see Table).

of (1) with toluene

(110 g) were co-pyrolysed

C6F11H requires

with traces

(1 g) by semi-preparative

in the ratio 55:45 attributable

able by the CF3-CF3

proportions.

(P205) and

gas chromatography

(6a and b) nc (.71 g), b.p. 94'C (Found: C, 19.9;

Br, 22.1; F, 57.9% M 260/262).

those

Analytical

(>90%) component

Br, 22.1; F, 58.2% M (mas spec.) 260/262.

components

When all

P 1:6, 80°, N2, 1.5 dm3 h-l) gave E and Z 2-bromo-undeca-

fluoro-3-methylpent-2-ene

of peaks

solution.

layer was separated

(14.9 g) was dried

in vacua by trap to trap transfer.

products.

The products

Any volatile

off and the residue was

sodium metabisulphite

had been removed

tube at 35O'C

of 5 hr.

in liquid air.

(less than 1 g) was allowed to evaporate at O-10" with precooled

(25.8 g) and bromine

added to the pyrolysis

in a glass trap cooled

(5a and b)

sample.

The oxiran

of (1) with bromine

(87 g, 28 cm3) were simultaneously

(TFE tetramer)

an authentic

In a similar experiment

to the

(63 g) gave (7a) and (7b) (15.9 g)

NMR DATA

Chemical Shift

Compound

a b CF3CF2

Assignment

Coupling

19F 'c=c

CF ' c3

-56.1

yBr

C

-59.3/60.1 'CF d3

(6a)

C

-80

q Jac 8 Hz

-107.5

q Jbc 22 Hz

l9F -58.4

a b CF3CF2

qt Jbc 23 Hz

-59.3/60.1 'c=c

CF ' c3

-79.9

'Br

-103.0

(6b)

a

Rel. Int.

6.35

d

b

cF3cF2.,

_ ,cF3 c-c

C:3'

= 7.5 Hz

-63.8 -82.9 -110.8

1H 6.25 H

cq JHd 7.5 Hz

19F

'CZC' 'CF d3

(7b)

cq JHd

-59.2

(7a)

CF ' c3

8 Hz qq Jbd 20 Hz

19F

'H

a b CF3CF2

C

st Jac = Jad =

-62.3

e

-62.7

C

-87.1 -116.1

q

Jac=

q Jbc

6 Hz

= 10 Hz

(Cor.tinued overleaf) -----

82 TABLE

(Cont.)

Chemical Shift

Compound

Rel. Int.

Assignment

-64.1

2

e

s

-74.1

3

C

C

-83.3

3

a

C

-121.5

2

b

-189.4

1

d

+57.3

1

h

-52.9

3

C

-69.3

3

f

Coupling

19F a

b

cF3cF2\ fl e c CF - C - c - CF2Br 3/ F d (8)

19F h a b CF3CF2\

F\ ,C=O

/ CF

e

c=c

/

d

CF2CF3

Lc

3

F’

C

'CF f3

CAB J "'AB

300 Hz 4'180 Hz C

C

cd J = 60 Hz C

-79.3

3

a

C

-79.6

3

d

C

-103.1

2

b

C

-115.9

2

e

CAB

-174.2

1

4

C

19F 9 a b CF3CF2

CF

F\ / \ c=cA

’

C3

+56.4

C

C:,

-57.4

C

e d CF2CF3

-68.9

C

‘c=o F' (l!b)

ii iv v 0

b

a

;F2cF3 i iii vi

-77.7

C

-78.1

C

-103.1

C

-115.5

CAB

-172.4

C

lH 1.27

5

i ii iii

C

1.88

6

iv v vi

C

-82.5

3

a

s

-122.3

2

b

19F

dJbi

145 Hz

83 Pyrolysis oxiran

(2)

of perfluoro-2-(l-ethyl-l-methylpropyl)-2-(l-methylpropyl) The oxiran

(10 g) was pyrolysed

(3 dm3 h-I ) at 330' over 3 hr. trap cooled

in liquid air.

CF3COF) were the residue g.1.c.

to be mainly

one component.

successively

to give a fluorocarbon

(0.63 g) by semi-preparative

F, 55.4; Br, 21.4%.

The oxiran

with

an

CBrFl10

(14 g) and bromine

with 25% sodium metabisulphite

gas chromatography

Separation

afforded

solution

of a sample

(i) l-bromo-

(8) nc (0.27 g), b.p. 89'C requires

(37 g,

(2 dm3 h-l).

(Found: C, 18.9;

C, 19.1; F, 55.4; Br, 21.2%); (9) (0.25 g) identical

to an authentic

[5].

Co-pyrolysis with toluene

The oxiran

of (2) with toluene

(12.3 g) was co-pyrolysed

(97 g) at 330-34O'in a stream of nitrogen

(7.8 g) was shown by analytical two components.

fluoro-2-methylbut-l-ene

Separation

Co-pyrolysis

of a portion

to authentic

(4.0 g) were heated together

for 24 hr.

The products

The oxiran

solid (3 g).

by semi-preparative

I9 F n.m.r.

(4.24 g) of the

gas chromatography

spectroscopy

(ii) pentafluoroethylcyclohexane

(Found: C, 47.0; H, 4.8; F, 47.0%.

(2) (24.6 g) and

in vacua to give a clear

A portion

indicated

CloF180 a mixture

(lla and requires of E

(12) nc (0.3 g), b.p. 114'C

C8HllF5 requires

C, 47.6; H, 5.4;

(iii) perfluoro-3-(3-methylpentyl)-2-(2-butyl)ketene

(13) (1.1 g) [12]; (iv) unreacted

to give

fluoride

llb) nc (1.7 g), b.p. 116'C (Found: C, 24.8; F, 71.8%.

F, 47.0%);

(i) per-

[5].

(i) perfluoro-3-methyl-2-(l-methylpropyl)-pent-2-enoyl

and Z isomers;

of

in a sealed Carius tube at 175'C

(20.2 g) were distilled

(17.2 g) and a polymeric

C, 25.1; F, 71.5%).

The

to consist

(1.25 g) afforded

samples

of (2) with cyclohexene

cyclohexene

liquid was separated

(2 dm3 h-l).

gas chromatography

(3) (0.25 g) and (ii) 3H-perfluoro-3-methylpentane

(10) (0.32 g) both identical

ketene)

showed

by semi-preparative

of nitrogen

layer (11.43 g).

(ii) 3-bromoperfluoro-3-methylpentane

liquid

in a glass

(mainly SiF4 and

(3) identical

at 330' in a stream

perfluoro-3-methylpentan-2-one

mainly

of nitrogen

gas chromatography

Purification

of (2) with bromine

The product was washed

product

components

and analytical

perfluoro-2-methylbut-1-ene

Co-pyrolysis

sample

in a stream

(7.9 g) were trapped

specimen.

12 cm3) were co-pyrolysed

and water

The volatile

allowed to evaporate

afforded

authentic

The products

starting

material

(hexamer(0.3 g).

84 Reaction The ketone dry ether

of l-bromoperfluoro-3-methylpentan-Z-one

(30 cm3) at -1O'C.

to 15' over 15 min. unidentified residue

white

The mixture

After filtration

F, 18.3; N, 7.2%.

C4H6BrF2N0

Mass spectrometry

6.9%).

in vacua to yield

(14) nc (1.38 g), b.p. 176'C

in the correct

requires

and allowed to warm

a small amount of an by vacuum transfer.

The

N,N-dimethylbromodifluoro-

C, 23.8; H, 3.0; Br, 39.6; F, 18.8; ion peak at m/e 201/203

atom being present.

REFERENCES

1

2

P.L. Coe, A. Sellars,

Part 3. 3,

P.L. Coe, S.F. Sellers,

J.C. Tatlow,

E.P. Moore,

U.S.P.

4

P. Tarrant,

C.G. Allison,

Revs.,

3338978,

P.L. Coe, S.F. Sellers,

1983,

G. Whittaker,

1967.

K.P. Barthold,

J.C. Tatlow,

G.B. Barlow,

J.C. Tatlow,

G.B. Barlow,

M. Stacey,

E.C. Stump,

Fluorine

H.C. Fielding,

Chem.

G. Whittaker,

J. Chem. Sot., 1952, 4695;

J.C. Tatlow,

G.G. Yakobson,

P.L. Coe, A. Sellars,

ibid, 1955, 1749.

Synthesis,

J.C. Tatlow,

J. Chem. Sot. Chem. Comm., 9

H.C. Fielding,

Chem., 1981, 18, 417.

V.E. Platanov, 8

Chem.,

1971, 5_, 77.

J. Fluorine 6

J. Fluorine

1, 1983, 1957.

3

5

J.C. Tatlow,

102.

J. Chem. Sot. Perkin

1976, 6, 374.

H.C. Fielding,

1982, 362.

P.L. Coe, I.R. Owen, unpublished

in

(Found: C, 23.9; H, 2.8; Br, 40.1;

gave a molecular

ratio for one bromine

of dimethylamine

was stirred

to remove

solid, the ether was removed

(3.4 g) was distilled

ethanamide

N,

with dimethylamine

(5.7 g) was added over 15 min to a solution

results.

G. Whittaker,