The reaction of secondary perfluoroalkyl iodides with zinc

297

Journalof Fluorine Chemistry. 6 (1975) 297 310 0 Elsevier Sequoia S.A.,Iausanne ~ Printed intheNetherlands

Received: January 15,1975

THE REACTION

T.M.

OF SECONDARY

KELLER

Department Florida

and PAUL

PERFLUOROALKYL

IODIDES

WITH

ZINC

TARRANT

of Chemistry,

University

of Florida,

Gainesville,

32611

SUMMARY

Evidence

for the existence

the reaction been

obtained.

bimolecular surface tion

of secondary At high

homolytic

to yield

is carried

mechanism

the substrate

perfluoroalkyl concentration

type reaction

dimers

appears

out under

appears

of two mechanistic

dilute

with

of secondary of the iodide

conditions, This

zinc has a

on the zinc When

an ionic

paper

for

iodides,

to be preferred.

to predominate.

itself

iodides

pathways

also

the reactype

shows

that

can influence

the reaction

route.

et al. showed1

that primary

fluorocarbon

INTRODUCTION

In 1957 Miller iodides

react

hydride

or the coupled

the reaction

with

was

zinc to give olefin, product.

indicated

between

n-heptafluoropropyl

solvent

or in the presence

methylene

chloride

caused

reaction

found'

that

or ethyl

at a lower

That

organozinc

solvent

iodide,

plays

a role

by the fact that no reaction iodide

and zinc

of non-donor

heptafluorobutyrate temperature.

1-heptafluoropropyl

iodide

of

such as benzene, whereas

Chambers gave

occurred

in the absence

solvents

in

dioxane

et al. in 1961

a 96.5%

yield

of the

298

coupled

product

when

subjected

presence

of mercury.

RESULTS

AND DISCUSSION

During l3 with Four

the reaction

of these

compounds

irradiation

in the

of 1,2-dichloro-4-iodoperfluoropentane

five fluorine-containing

zinc,

perfluoropentane

were

compounds

identified

2, l,l,l-H,H,H-5,

were

as 2-H-4,

formed.

5-dichloro-

6-dichloro-3-trifluoromethyl-

l- and meso-1,2,7,8-tetrachloro-4, 1, cJ, -

perfluorohexan-2-one 5-bis

to ultraviolet

(trifluoromethyl)-perfluorooctane CF2C1CFC1CF2CFICF3

Zn Ac20, CH2C12l or CH3C02Et,

1 -.

4. CF2C1CFC1CF2CFHCF3 2

CH2C12

Leg. 11

CF

+ CF 2 ClCFClCF 21CF!CH 3 +

(CF2C1CFClCF2&F:2

CF3 4 -

3 + unidentified The yield

of each

conditions

TABLE

1

product compound

(see Table

Reaction

of 1 with

(Relative

CH2C12

Zn, Ac20,

CH2C12

Zn, CH3C02Et,

found

At longer

Zinc under

to depend reaction

on the reaction times

Different

and higher

Conditions

Ratios)?

Conditions Zn, Ac20,

1).

was

b c

CH2C12

C

Unidentified Product

2 -

3

4 -

18

16

55

11

25

31

32

12

68

4

21

7

aRelative ratios are weight percentage obtained from peaks using a thermal detector. b Addition of 1 in one sum. CAddition of 1 dropwise.

integrated

299

at least

temperatures, probably

from the

Besides proven

three

other

slow dehalogenation

spectral

by chemical

The reaction

means.

in hexamethylphosphoric

quenching

in water.

lDuring

the reaction acetic

amounts

base,

acetyloxy

zinc,

and ethyl

2 upon

[eq. 21

The two coupled means.

dioxane

methyl)-1,7-perfluorooctadiene The mass

spectra

with

the exception

ular

fragments.

slightly

which

indicated

The coupled

obtained

were

on a

identical

of some of the molec-

and 19F nmr spectra

to be formed

atom.

the reaction

were

certainly

SN2 reactions

carbon

during

two mechanisms

4 is almost -

since

fluorinated

were

that

product

type mechanism'

2, appear

(trifluoro-

were

different.

The results zinc

abundance

the infrared

Moreover,

zinc dust

be separated

of the two diasteromers

of the relative

not be separa-

4, 5-bis

could

a

to the

of 4 with

and meso-

5 which -

being

compared

4 could -

reaction

c-,1-

anion,

group

products

from two acetyl

but in different

the ethoxy

However,

yielded

formed

acetate,

is not as good a leaving

ted by analytical

highly

(HMPT) yielded

2 -

2 was

Apparently,

1).

anion.

in refluxing

of 1 with

anhydride

(see Table

stronger

with

was

of 1 and potassium

H2°

-

formed,

components.

of each product

triamide

K+ CF2C1CFC1CF2CFCF3

were

HMPT

sources,

glpc.

compounds

of the main

the identity

means,

hydroxide

KOH

volatile

formed

The noncoupled

by an ionic mechanism

occur

products,

(eq.3). Ac20

a

CF2C1CFC1CF2CF(CF3)ZnI

operative.

by a radical-

do not readily

the two mechanisms

CF2C1CFC1CF2CFICF3

probably

of 1

at a 2 and

Therefore, 3 leq. 31

300 depending

are competitive, Since

the ionic mechanism

lute conditions, synthesizing iodides.

on the reaction

we decided

The reaction

anhydride,

Apparently,

unfavorable

in the non-donor,

radical

to prepare

pentan-3-one

compounds

very

slowly

formations

1

solvents.

iodide

led to the rapid

to yield

10 is surprising. -

to

are highly

-9 in

evolution

The fact that 9 does not react

anhydride

zinc

in an extremely

perfluorinated

anhydride

of

anhydride-chloro-

2-perfluoropropylzinc

dioxane-perfluoropropionic 8. -

6 with -

proceeded

and ionic

di-

perfluoroalkyl

perfluoroacetic

volatile

low yield.

of perfluoropropene

secondary

anhydride

two unidentifiable,

perfluoropropionic

from

under

the feasibility

of 2-iodoperfluoropropane

form and perfluoropropionic

An attempt

to predominate

to investigate

perfluoroketones

in perfluoroacetic

yield

appears

conditions.

with

2-trifluoromethylperfluoro-

The carbonyl (CF~CF~CO) 2o

Zn CF3CFICF

3

dioxane (CF3CF2C0)20

6 -

B

CF3CF(CF3)CCF2CF3

CF3CFCF3

l

10 knI

1‘

CF3CF=CF2 8 -

9 group

in perfluoropropionic

and thus more some other solvent

phenomenom

and could

anhydride nished

reactive

to acetic

the reaction

the reaction

using

sieves,

that

be more anhydride

Dioxane

the carbonyl

electrophilic unless

is a donor-type

groups

of the fluorinated

its reactivity

is greatly

dimi-

anhydride.

of 5 with anhydrides

ethyl

should

9 than acetic -

is operative.

solvate

and perfluoropropionic

molecular

toward

to such an extent

relative

Since

anhydride

zinc was

in both perfluoroacetic slow, we decided

trifluoroacetate,

as the solvent.

which

The reaction

to repeat

was dried proceeded

over rapidly

301 to yield

2-H-perfluoropropane

perfluorobutane

11

(see Table

Zn ._ CF3C02Et

CF3CFICF3

7 and 2, 3-bis 2).

CF3CFHCF3

6 -

2,

3-Bis

TABLE

+ I (CF3)2CF12

7 -

11 -

Ctrifluoromethyl)-perfluorobutane

previously2

by irradiating

11 has been -

5 in the presence

2 Reaction of 6 with (Relative Radios)

(trifluoromethyl)-

Zinc in Ethyl

Conditions

of mercury.

Trifluoroacetate

7 -

11 -

En, C03CF2Eta

46

54

En, CF3C02Et b

77

23

a

Reactant

added

To shed more zinc,

Reactant

with

methylene

zinc

in both

chlorine.

fluoropropene again

8 was -

the main

added

light on the reaction

1-chloro-2-iodoperfluoropropane

treated

was

b

in one sum.

From

acetic

but a second

to be 1-chloro-2-H-perfluoropropane

13 from -

was also

The formation

formed

is probably incorporation

in a small amount.

due to small

amounts

was used,

which

of peroxides. 1,5,6

Yi=;

-

s

(100%)

8 -

spectrum,

of 13 in dioxane Apparently,

Dioxane

T------*

per-

was believed

its infrared

of the zinc

CF3CFICF2C1 12

and

chloride

dioxane

product,

with

anhydride-

anhydride-methylene When

iodides

synthesized4

and acetic

the sole product. product

dropwise.

of secondary

12 was -

dry dioxane

prepared

CF3zHz

302 between

the carbon-iodine

abstraction to yield

of iodine

the coupled

The preferred zinc could

1

for primary

tant.

for the reaction

to either

14 with -

has been

indicating

the carbon-zinc

to 12 supports

to primary

when more

products

bond

the steric

will

extreme

is covalent coupling

of 14

interaction

anion

than one mechanistic

zinc

under

of secondary

perfluoroalkyl

the solvent

except

The observed

stability

effects.

and n-perfluoro-

E,7

to be inert

iodides.

the greater

relative

which

shown

that

perfluoroalkyl

Thus,

of 12 with

of 1,2-dichloroiodotrifluoroethane

Moreover,

8

by zinc

or steric

the concentration, mine

of reactants

electronic

is in contrast

anions

the radical

product.

ionic pathway

iodide

conditions,

cept.

over

1,2,3,4-tetrachloroperfluorobutane

propylzinc

which

is favored

from two molecules

be attributed

The reaction yields

bona

con-

perfluoroalkyl

is surely

pathway

and the substrate

impor-

is possible

seem to deter-

be formed.

EXPERIMENTAL

1,2-Dichloro-4-iodoperfluoropentane literature

procedure,

B.P.

58-61

1 was prepared

(20 mm);

reported

by a

58.5-60.5

(20 mm).3

The reaction Chloride.

-To a 25 ml,

(0.011 g. atom)

added

Zinc in Acetic

three-necked

of granular

and 3 ml of acetic was

of 1 with

anhydride.

zinc,

Anhydride-Methylene

flask was added 3 ml of methylene

Compound

in one sum and the reaction

0.71 g chloride

1. (5.1 g, 0.011 mol)

mixture

was heated

at 40-

303 45' for tion,

53 hours.

After

removing

dilute

hydrochloric

ing solution

was allowed

was washed

with

with

neutral,

sulfate.

trated

residue

had been

sodium

Analysis

that

five

solution

and was dried

(glpc relative

indicated

ratios)

component (NC) 2

cm -'

(C-F;m/e

267

ref):

-14.1

(18% relative

54.0

over

anhydrous

of the concen-

and elemental

proposed

mass

as described

ratio);

; “F

ir

nmr

-2.3

compounds

19

(CFC13),

77.1 ppm

having

tive ratio):

F nmr spectra

was

however, with

by an independent

identified.as

2930

(neat)?

(C-Cl); m/e 72.3

(CFCl, multiplet), 'H nmr

Anal.

(CFH, multiplet)

consistent

were

TFA

40.9

not be obtained;

could

It was also made

component

ir

665 cm-l

mass,

the proposed

external

a low heat of vapor-

the

method

l,l,l-H,H,H-5,6-

dichloro-3-trifluoromethylperfluorohexan-2-one

infrared,

1375-1130

(gas):

below.

The second

ref):

5-dichloroper-

(CF3, multiplet),

volatile,

analyses

and

structure.

as 2-H-4,

(CFCl, multiplet),

was extremely

the infrared,

plet) :

until

fluorine-containing

identified

(CF2C1, muliplet),

compound

ization

was

[M+(C135)-C135J

(CF2, multiplet),

CFC13

layer

formed.

fluoropentane

712,

and the result-

The organic

bicarbonate

bisulfite,

zinc by filtra-

added

to stir overnight..

saturated

The first

This

acid was slowly

10% sodium

sodium

the unreacted

(C-H), 1740

309

and

19

2.46

"F

nmr

(C-F),

(neat,

(CF2C1, multiplet,

(CF2, multiplet),

(neat, TMS ref) : proton,

63.3

(NC) (16% rela-

(C=O), 1300-1100

IM+(C135)-C1351;

(CF2, multiplet), 106.1

2

168.9 ppm

(CF multiThe

(CH3, doublet).

F nmr spectra

were

133

consistent

with

structure. Calcd

for C7H3FgC120: Found:

C, 24.4: H,0.87; C, 23.98;

Cl, 20.6

H, 0.81;

Ci, 20.40.

304 The third

and fourth

components

were

identified

as -d,l-

and

meso-1,2,7,8-tetrachloro-4,5-bis(trifluoromethyl)-perfluorooctane 4 (55% relative (C-Cl); m/e

ratio);

567

(neat):

IM+(C1351-C135J.

not be separated, Anal.

ir

19

the

Calcd,

1280-1120 Since

for C10F18C14:

identified.

component

According

the two compounds

could

F nmr was not obtained. Cl, 23.48

Found: The fifth

(C-F), 690 cm-l

Cl,

22.54

(11%) was extremely to its infrared

volatile

spectrum,

and was not

it is a satura-

ted compound. A second g. atom)

of granular

of methylene resulting mol)

reaction

zinc,

chloride

mixture

into a 50 ml,

dropwise

for 24 hours

product

mixture

formed

but in different

The Reaction Acetate-Methylene containing acetate g

1.7 g

at the above

a period

-To a 100 ml,

(0.026 g. atom)

of 1 at 48-50'. temperature

The

(0.014

of 12 hours.

After

was worked

up

(g1p.c) of the concenwere

(32%) and

(12%).

Chloride.

usual

and 6.0 g

The

that the same components

Dilute

Workup

and 20 ml

2 (25%), 3 (31%), 4 -

amount:

(0.014

flask.

mixture

of 1 under

for 24 hours. manner.

(reflux)

Analysis

indicated

and 30 ml of methylene

(0.023 mol)

over

as above.

trated

product

to 43“

0.91 g

anhydride

three-necked

at 43' the reaction

by the same procedure

unidentified

out by placing

5 ml of acetic

was heated

of 1 was added

heating

was carried

Conditions

of granular

chloride

and concentration

same components

Zinc in Ethyl

three-necked zinc,

was added

The resulting

for 24 hours

with

flask

30 ml of ethyl dropwise

mixture

was heated

and then at reflux was achieved

10.2

(62')

in the

as in the preceeding

experi-

305 ment

were

formed

in the following

4 (21%) and unidentified C4%), _

The Reaction 100 ml, 50 ml

of 1 with

roundbottomed

of HMPT

resulting

solution

poured

into

layer

yielded

polymeric

was heated

4.0 g

during

was added

ml of diglyme. CO.033 mol)

To this

The temperature

was dlstilled

from

clog) was washed

These

water

The product

was

were

were made

from the

simplicity

of 5B. for 5A

(C-F): m/e and -3.4

462

19

plet).

separated

ir

(M+&35);1gF

(CF3, multiplets), complex

nmr 11.6

dust

was heated

over

19.9 g

The product

anhydrous

sodium by qlpc.

(5A) - and meso

of 5A and the

(=CF2),

1350-1250

cm

-1 -5.9

TFA ref):

(F in = CF2, quartet), 108.4

(5B)-4,

The assignments

(CFC13, external

multiplet),

and 150

at 140“

into two components

1770

identical

and the product

at 137-138'.

as d, I

some

zinc.

dropwise

7-perfluorooctadiene.

(gas):

with were

of zinc

increased

and was dried

and

-To a 500 ml, three-

F nmr due to the complexity

(NC) :

(CF2 and F in = CF~,

vessel

identified

5- bis(trifluoromethyl)-1,

mixture

The

cooled

of 1 with

was added

was then

the reaction

with

components

Data

CO.12 g. atom)

hot solution

along

spectra

Zinc Dust.

of I,

of the organic

96-lOOa,

the reaction

-To a

hydroxide.

for 24 hours,

and mass

of 4 and the resulting

for 1 hour.

sulfate.

7.8 g

(0.036 mol)

Distillation

of 4 with

2 (68%), 3 -

in HMPT.

of potassium

at 70-75O

The infrared

was produced

flask

15.7 g

(33%) of 2_, b.p.

The Dechlorination necked

Hydroxide

added

ml of ice water.

la0

material.

to 2 which

Potassium

(0.054 mol)

ratios:

(7%).

product

flask was

and 3.0 g

relative

ppm

28.8

(2 CF,

multi-

306 A&.

Calcd

Data

for 5B

(C-F); m/e

462

ClOFl8:

F, 74.97

Found:

F, 74.88

(NC):

(gas) :

ir

(M+ C135);

1770

lgF nmr

(CF3, multiplet),

7.1 and 25.7

28.8

(CF2, multiplet),

97.3

The

tent with

infrared,

the proposed

Anal.

Calcd

Perfluoroacetic -TO a 100 ml, of granular

F, 74.97

Found:

F, 74.94

of 2-Iodoperfluoropropane

Anhydride

(0.051 mol)

and Pentafluoropropionic

three-necked

flask

was added

mixture of 5 was

was then

was heated slowly

stirred

to 39O

added

anhydride,

(CF,

were

consis-

Zinc

in

over

and trace

b.p.

amounts

Anhydride.

3.43 q

(0.053 q. atom)

anhydride.

(reflux) a period

for an additional

Cglpc and IR) of the distillate, acetic

6 with

zinc and 30 ml of perfluoroacetic

heterogeneous

mixture

Spectra

ppm

structures.

C10F18:

The Treatment

-1

and multiplet),

and 107.9

and lg F nmr

cm

TFA ref):

(=CF2, triplet

CCF, multiplet), mass

1350-1250

(CFC13, external

-7.9

multiplet).

(=CF2),

and 15.1 q. of 12 hours.

12 hours.

36-39',

showed

of two other

The

The

Analysis 5, perfluoro-

compounds

to be

present. This

distillate

(O.Q49 g. atom) The reaction Analysis

of zinc dust anhydride, ous mixture

slowly

of granular

mixture

showed

Another

was

reaction

only

a higher

trace

amount

of 3.2 g

solvent.

to 60-65',

(38-39')

for 15 hours.

of two new compounds.

using

(0.024 mol)

boiling

was heated

at reflux

was attempted

and, 13.2 q

to a mixture

zinc and 25 ml of dry chloroform.

was heated

again

added

2.6 q

(0.040 q. atom)

of pentafluoropropionic The resulting

7.2 g

(0.024 mol)

heterogeneof 6 was

307 slowly

added;

and the reaction

(57") for 12 hours. cated mostly

Again,

starting

The Reaction

added

2.69

and 13.2 g resulting 6 was -

Anhydride.

added

distillation dioxane.

Most

Analysis 5

was

glpc

mixture

was

The

to 45-50°,

No reaction

increased

to 78-80'

had disappeared.

material

flask

30 ml of dry dioxane

heated

of 4 hours.

Zinc in Ethyl

flask

was heated

heated After

was added

showed

and

was (reflux)

Fractional

anhydride mainly

and perfluoro-

were

that

During

The first

compound

(gas):

also produced

collected

two compounds

2980

was

had been

5 with

of 5

the reaction

trifluoroacetate and distillation,

trap.

Analysis

by

formed.

as 2-H-perfluoropropane

(C-H) 1380-1120

2-perfluoropropyllithium

(0.049 mol)

Ethyl

in a cold

of

The hetero-

the reaction

identified

by treating

(0.051 g atom)

was completed,

for 20 hours.

by distillation.

components

3.3 g

and 14.7 g

the addition

-To

Trifluoroacetate.

trifluoroacetate.

to 55-60°

at 55-60'

indicated

quenching

indi-

Zinc in Dioxane-

three-necked

pentafluoropropionic

of 6 with

added.

7 (77%); ir L was

mixture

anhydride.

nitrogen,

was then

zinc and 20 ml of ethyl

was removed volatile

with

of the trapped

three-necked

slowly

content

of zinc dust,

a period

only

at reflux

(99%) to be present.

a 100 ml,

geneous

6 with

-To a 25 ml,

of the zinc dust

yielded

The Reaction

granular

over

The temperature

for 10 hours.

of the reaction

of pentafluoropropionic

was flushed

heated

to be present.

(0.040 g. atom)

mixture

observed.

propene

materials

CO.042 mol)

slowly

analysis

was then

of 2-Iodoperfluoropropane

Pentafluoropropionic were

mixture

cm -'

(C-F).

Compound

n_-butyllithium

which

was

formed

and by

with water.

The

second

compound

was

methyl)-perfluorobutane (C-F); m/e

319

(M+-F);

(CF3, doublet) trum matches A second zinc and 5

that

reaction

stirred

tive ratios)

procedure. room

4

was

1.3 g

added

added

6.5 g

30.6 g

The resulting

The

-7.2

F nmr

spec-

of granular

was carried

out.

Analysis

indicated

Zinc

compound

by glpc

that

(0.11 g. atom)

for 20 minutes

to be present.

to be perfluoropropene

mix(rela-

46% of 7 and

The first

peak

13 from -

zinc,

methylene

chloride.

one sum.

The temperature

at 25-30“

for 20 hours

peak

began

was

at

at 40-50°

material (-95%) was

showed found with to be

Anhydride-Methylene

flask was

to rise

by cooling

stirred

its IR spectrum.

added

anhydride

(20.1 g,

12 -

8

by a known

(-5%) was believed

5 ml of acetic

compound

zinc,

of its IR spectrum

Zinc in Acetic

three-necked

-To a 50 ml,

mixture

of the volatile

The second

of 12 with

of granular

and was then heated

by glpc

1-chloro-2-H-perfluoropropane

-To a 50 ml, three-

of 12, prepared

8 by comparison -

sample.

of granular

in Dioxane.

heterogeneous

two components

g atom)

19

in one sum and the resulting

(0.096 mol)

Analysis

Chloride.

-1

TFA ref.):

(0.020 g atom)

material

of 12 with

The Reaction

cm

9

for 35 hours.

for 10 hours.

an authentic

(CFC13, external

trifluoroacetate

was

1270z1130

(gas):

sample.

(trifluoro-

formed.

and

temperature

as 2, 3-bis

(CF, multiplet).

using

of the trapped

The Reaction

ml of dioxane

ppm

at 52-54"

54% of 11 had been

flask

nmr

of an authentic

7 ml of ethyl

ture was

(23%); ir

"F

and 112.2

(5.0 g, 0.017 mol)

necked

11

identified

in water.

Workup

(0.064

and 5 ml of

0.064 mol)

immediately

4.1 g

was added

in

but was kept was accom-

309

plished

by the usual method.

tile material be present. present

in the cold No other

dride,

reaction

zinc.

to -30 to -200 hours kept

at this

appeared

of the vola-

perfluoropropene.8 - to

besides

the solvent

was

was carried

out using

5 ml of acetic

anhy-

chloride,

and 2.1 g

(0.032 g atom)

of

and 10.4 g

heterogeneous

(0.033 mol)

reaction

temperature

and the mixture

Perfluoropropene

only

component

The resulting

no observable

showed

(IR and glpc)

vessel.

5 ml of methylene

granular

trap

organic

in the reaction

A second

Analysis

of 12 was

had occurred.

for 4 hours. was allowed

8 was the only

solution

Most

added.

After

The temperature

was

which

to room was

temperature.

formed.

ACKNOWLEDGEMENT

This research Force

Materials

Ohio;

J. K. Sieron

was

supported

Laboratory, was

in part by funds

Wright-Patterson

the project

from the Air

Air Force

Base,

officer.

REFERENCES

W. T. Miller, Jr., E. Bergman Chem. Sot., 79_, (19571 4159.

and A. H. Fainberg,

R. D. Chambers,W. K. R. Musgrave K., (1961) 3779. M. Hauptschein, M. Braid, E., 79, (1957) 2549. M. Hauptschein, M. Braid E., 83, (1961) 2495. R. N. Haszeldine,

and J. Savory,

and F. E. Lawlor,

Sot.,

J. Am.

J. Chem.

J. Am. Chem.

and A. H. Fainberg,

J. Chem.

3

of the zinc had dis-

to rise

product

was cooled

(1952) 3423.

J. Am.

Chem.

310 6

H. J. Emelius

and R. N. Haszeldine,

J. Chem.

SOC.,

(1949)

2948. 7

A. L. Henne 2334.

8

R. D. Chambers, Fluorine in Organic and Sons, 1973 ed., pp. 89-91.

9

R. D. Dresdner, F. N. Tlumac 82, (1960) 5831. sot -.'

and W. Postelneck,

J. Am. Chem.

Sot.,

Chemistry,

and J. A. Young,

77

(19551,

John Wiley

J. Am. Chem.