The i.r. and Raman spectra of 1-(chloromethyl)-4-fluorobenzene

SpectrochimicaActs, Vol. 31A, pp. 1605

PergamonPress, 1975. Printed in Northern

to 1610.

Ireland

The is. and Ranan spectra of 1-(chloromethy~~-4-fluopoben~ene W. A. SETH-PAUL Janssen Phermaceutica

Research Laboratories,

Beerse, Belgium

and H. SHIN0 (Europe),JEOL House, GrovePark, Colindale,London,England

JEOL

(Rec&&

3 September; rwi.xd 12 November 1974)

Abstra&-The i.r. and Raman spectra of I-(chloromethyl)-4-fluorobenzene (4-fluorobenzylchloride)have been measuredin the liquid state. The data are interpretedon the basis of 0, symmetryalthoughthe depolarization data suggestthat the moleculeis probablyof C, symmetry. ~~DU~O~

In the courseof studying the ix. and Raman spectra of some 1-(4-halophenyl)-4-chloro-1-butanones:

X

bCHzCH CR&3 2

which are important compounds with respect to several well-known drugs, we have started to investigate 1-(chloromethyl)-4-fluorobenzene (CMF) and 2-chloro-1-(4-fluorophenyl)-l- ethanone (CFE), the latter (~-~~oro-4-~uoro~etophenone) differing from CMF (4-fluorobenzylchloride)by a carbonyl group between the phenyl ring and the chloromethyl group. Preparation

of the sample

l-(C~oromethyl)-4-fluorobenzene was prepared according to the following reaction: F

halogen atoms. The local symmetry of the ring is, of course, C,, but it may also be that CMF has no symmetry at all in which case the C-Cl bond is twisted slightly out of the plane of the phenyl ring.

CH,OH+SOCl,

--f F

CH2~l+SO~+HCl

One mole of thionylchloride was added dropwise (1 hr) to one mole of 4-fluorobenzylalcoholand the temperature was raised slowly from 20% to 80%. The product was allowed to cool. Careful distillation by means of a Nester-Faust spinning band column (66’/10 mm) yielded CMF of 99.5% purity as shown by gas chromatography. Symmetry If CMF is assumed to have C, symmetry, it may by that (a) the phenyl ring and the chlorine atom are coplanar or [b] the phenyl ring is perpendicular to the plane of symmetry passing through both

There will be thirty-nine fundamentals distributed among (26a’ + 13a”) vibrational species for C,(a) or [22a’ + 17a”] for the C,[b] conformation and these modes should be active both in the i.r. and the Raman. The a‘ modes have their dipole transitions in or parallel to the plane of symmetry and will be polarized. The a” modes have their dipole transitions perpendicularto the plane of symmetry and should be depolarized with respect to Raman radiation. The thirty-nine vibrations can be olassifledinto fourteen (13a’ + a”)/[%’ + 6a”] stretches and twenty-five (13a’ + lZa”)/[14a’ + lla”] deformation modes where the assignmentsbetween round/ square brackets refer to conformations C,(a)/C#] respectively. It must however be emphasized that many modes are most likely considerably mixed precludingin fact the use of terms such as stretching or deformation because it might well be that e.g. a ring stretch also implies a certain amount of CH defo~ation and vice versa. Thus with some assignments a certain vibration turns out to be predominantly a stretch or a deformation whereas in others this might not be the case. And therefore, the description of the fundamentals used in this paper is a formality and chosenmerely for the sake of convenience. It should in fact be interpretedas an approximate description of the true state of affairs particularly with the so-called X-sensitive vibrations.

1605

1606

W. A. SETH-PAUL EXPERIMENTAL

Infrared

and

The spectrum

of CMF was recorded in a NaCl

cell and between CsI plates using the model of Perkin-Elmer

with dry air flushing.

225

The instru-

ment was calibrated by interpolation from external water vapour, methane and ammonia bands.

Raman

spectrophotometer

with a CR-2 argon ion laser (4880 A). tion measurements

were made

equiped

Depolariza-

using a polarizer

plate.

we have placed The

spectrum

bands

at 1221 and

are

vantage

the

fundamentals,

ad-

was taken from papers dealing with the

vibrational

spectra of related compounds

4-fluoroanisole

[l,f],

4-fluorotoluene

such as

[4]. 4-fluoro-

aniline [6] and CMF recorded in the far i.r. [6]. The i.r. and Raman frequencies, intensities and depol~zation

ratios are given in Table

fundamentals

and their approximate

4-fluorotoluene methyl

1.

The

description

in the i.r. spectrum

of

cm-r which we assign

to vr, vz, va and v&(vCH)a’. The weak band at 3115 cm-r is considered to be the combination band

vs)A’ which has no scattered

(v, f in the

Raman.

The

in plane

%3- v17 and vr,,(KH)a

quencies 1305,

1160,

CH

counterpart defo~atio~

are assigned

There

are four bands in the i.r. spectrum of CMF of which the one at 851/848

cm-l

(i.r./Raman)

is attributed

823 cm-l ($H)a”

band

are

at

823 cm-r.

at 940,

assigned

respectively.

to

912,

Therefore, 836

and

the

~830/

vss, vsO, vgl and

The 823 cm-l

Raman

vss

band

vr4 absorbs as

probably

overlapping

All four in plane ring deformations polarized with confo~ation

C,(a).

should be

With C,[b]/C,,

symmetry,

only two/three of these modes should be

polarized.

These modes

are found to absorb

at

842, 728, 638 and 455 cm-r in the i-r. spectrum of 4-fluorotoluene

[4].

Analogous

bands at 851/S48,

to these data, the

7321728, 6361628 and

are assigned to vre, vse, vsz and vsa The bands are polarized respectively. (+)a’ which favours C,(a) symmetry. The X-sensitive

fundamentals

associated

the in plane bending of the F atom/Me have

been localized

spectrum

at 424/313

of 4-fluorotoluene

there is no doubt to v24(6Q’)a’

that

with

carbon atom

cm-r

in the i.r.

[4, 61 and therefore,

the i.r./Raman

bands at

can safely be attributed

and v25(6#7)a’ respectively.

There are three modes associated with ring out of plane deformations expe&ed to be (depolarized)/ [polarized] on account of Csu, C,(a)/C,[b] symThese modes are found to absorb at 4-fluorotoluene

bands

placed

95.

long wavelength side of the band. i.r./Raman

accordingly

In the i.r. spectrum,

metry.

Moreover, there

as-

that is the v+P at the

have

a strong band at 1225 cm-l

However, the intense 836 em-r band to vr,(S+)a’. in the i.r. spectrum is quite unsymmetric at the is a Raman

we

4211418 and 3021303 cm-l

the fre-

1097 and 1016~m-~.

vibrations

and v~~(v#C)a’ at 1221 and 1207 cm-l

4741470 cm-l

>3000

to be assigned

[4] the X-sensitive

frequency,

in Figs. I and 2 and the Raman spectrum in Fig. 3.

CH vibrations

bands in the Raman

1207 cm-l

group against the phenyl ring have been

i.r./Raman

There are four bands

which

sociated with the stretching of the flourine atom/

are given in Table 2. The i.r. spectrum is depicted

CMF at frequencies

polarized

to either v~~(v~~)a’ or wrs(vQIC)a’. However, sincein

respectively. of

In the

vs, v7, vs, vn, and

v~~(v~)~’ at 1607, 1602, 1512, 1416 and 1295 cm-l respectively.

higher

Assignments most

in the

however,

bands should be depolarized.

i.r. spectrum,

v~*(v~~)a’

assigning

conformation

be polarized symmetry,

placed at 122411214 cm-r, RESULTS AND DISCUSSION

31.

C,[b]/C,,

With

[three]/two

should

There are two polarized

The liquid was measured in a O-2 ml cell on the

In

Raman.

Assuming

1300 em-r.

all five bands

favours the C,(a) conformation.

Raman spectra JRS-Sf

around

C,(a),

spectra

JEOL

and H. SHINO

695,

502

and

i.r. spectrum i.r./Raman 624/525

404 crnpx in the

i.r.

spectrum

of

[4], and at 694 and 500 cm-l in the of 4-~uorobenzenethiol

spectrum

of CMF,

171. In the

there are bands at

and 421/41S cm-1 which may be assigned

is polarized which would agree with G,[b] symmetry

to vas and v~~(v~)a~ respectively, thus v~~(~#~)a’ and vs6(v4)a” have been assigned similar frequcn-

of the molecule.

ties.

Ring vibrations The 1600,

difficult

ring vibrations

fluorotoluene

in C-fluoroanisole

and

have been observed between

1602-1593,

The bands are polarized which would indicate

C,[b] symmetry.

1513-1600

and 1450-1430

4-

1625cm-’

to

absorb at CMF,

-700

however, Thus

690 cm-l.

The third fundamental

locate

is more

because v,,(vCCl)a’ starts The Raman spectrum cm-l. displays vs4(v+)a”

to of

a shoulder around either coincides with

T a b l e 1. V i b r a t i o n a l s p e c t r u m o f 1 - ( c h l o r o m e t h y l ) , 4 - f l u o r o b e n z e n e Infrared* Liquid 3899.8 3799.8 3679-7 3640"0 3585-0 3195"1 3115"2 3073.3 3045-1 3005-2 2965.2 2870"3 2795"4 2705"3 2660"2

Raman Liquid

Intens.

p (v s + vl.)A' = 3896

vw vw vw

(vs + v2z)A" ~ 3680 (v4 + v22)A' ~ 3640 (vl + v~a)A' ~ 3589 2 v ~ ( A ' ) = 3204 (v, + v~)A' = 3119

vw vw vw vw w w w w w vw vw vw

3208

1

3071 3053 3006 2966 2870

100 8 17 43 6.2

2570'4 vw 2445.4 vw 2258.6 vw 2230.4 vw 2070'6 vw 1894"6 w 1764"7 w 1702"8 w 1606"6 m 1602.3 m 1512'2 s 1464"1 w 1445"1 w 1416.1 w 1305.1sh 1295'2 w 1266"2 m 1225-0 s s sh m w m sh w

0

vx(vCH)a',vz(vCH)a' va(vCH)a" v~(vCH)a' v~(v.CH~)a"

0"14 0"70 0.30 0"04 0

v~(v,CH~)a'

(v~ + vi~)A" = 2 7 0 4 2622 2603 2585

1160.1 1149 1097.0 1048.0 1016"1 951'8 939"8

Assignment~

1"5 1-5 1"5

(v 6 % r l s ) A ' = (Vie "~ Vls)A" ~ 2623 (Vll "~- V l 2 ) A ' ~ 2 6 0 0 2 v l ~ ( A ' ) = 2590 (rio % vxe)A' = 2 5 7 6 (v e + v s l ) A " = 2443 (v16 + vlT)A' = 2257 (vt~ + vs,)A ~ = 2235 (vie + Vs0)A ~ = 2072 (v16 + vao)A" = 1892 (vl, + %0)A ~ 1762 2 v l . ( A ' ) = 1701

0 0 0

=

1607 1602 1508

19 2 2"7

0"67 0.70 0"50

1443 1418

3 0.5

0"67 0-75

ve(v~)a' v~(v~)a' vs(v~)a' 2v2o(A') = 1464 v.((~CH~)a'

vlo(v~)a' vtl((~CH)a' vx~(r~b)a' vls(~oCHi)a'

1293 1264 1221 1207 1158

2 43 67 16 26

0"70 0-27 0.02 0.10 0.23

1098

2

0'75

848

96

0"02

823 752 728 690 667 628

14 31 50 sh 57 19

0.04 0.21 0"27 0.12 0.68

vzl(vCC1)a' v~(e$¢)a"

525 470 418 360 303 204

17 4 1 25 5 19

0-25 0"20 0.29 0.26 0.28 0.40

v85(~¢)a" v23(($¢)a"

v14(vCF)a" vl~(v¢C)a' vl~(($CH)a' vz,(rCHs)a ~ vx~ ((SCH)a' 2 v s s ( A ~) = 1048 vt~((SCH)a' 2 v . ( A ' ) = 948? v , (~CI-I)a" vao( y C H ) a ~ vll (~b)a' vsl ( T C H ) a ~

911.7 850"7 835"5 830 756.0 732"0 669'0 635'1 597.0 524-1 474.2 421.2 355"0 302.1 204.1

s s sh sh s s sh vw m m m w w w

vs~(~,CH)a" vas(pCHz)a" v~o(~)a'

(X-sensitive) (X-sensitive)

(X-sensitive)

(X-sensitive)

vs,(~¢)a ~

(X-sensitive) (X-sensitive)

vz~(~¢F)a', va6(7¢)a" vs~ ((~¢F)a ~ v~6((~¢C)a" v.s(F¢C)a"

(X-sensitive) (X-sensitive) (X-sensitive)

vs6(¢$CC1)a" Vs. (TCHzC1)a ~ * vw = very weak, w = weak, m = medium, sh = shoulder and s = strong v = s t r e t c h , ($ = i n p l a n e b e n d , 7 = o u t o f p l a n e b e n d , ~o = w a g , ~ = t w i s t , p = r o c k a n d ~b = p h e n y l r i n g . See T a b l e 2 for a n a p p r o x i m a t e d e s c r i p t i o n o f t h e f u n d a m e n t a l s . 1607

1608

W. A. SETH-PAUL

and

H. SHINO

Table 2. Fundamentals of l-(chloromethyl)-4-fluorobenzene Species a’

a#

Activity

No.

Rpproxlmate description of fundamentals

R(p),i.r.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

CH stretch CH stretch CH stretch CH stretch CR, sym. stretch Ring stretch Ring stretch Ring stretch CH, bend Ring stretch CH in plane bend Ring stretch (Kekule) CH, wag “PFstretch $C stretch CH in plane bend CH in plane bend CH in plane bend Ring in plane bend Ring in plane bend CC1 stretch Ring m plane bend Ring in plane bend (dF in plane bend $C in plane bend CC1 in plane bend CH, antisym. stretch CR, twist CH out of plane bend CH out of plane bend CH out of plane bend CH out of plane bend CH, rock Ring out of plane bend Ring out of plane bend Ring out of plane bend $F out of plane bend (PCout of plane bend CH,C!l torsion

R(dp),i.r.

(X-sensitive) (X-sensitive)

(X-sensitive) (X-sensitive)

(X-sensitive) (X-sensitive) (X-sensitive)

(X-sensitive) (X-sensitive)

Assignment 3073 3073 3045 3008 2870 1607 1602 1512 1445 1416 1305 1295 1266 1225 1207 1160 1097 1016 851 732 669 635 474 421 302 2965 1149 940 912 836 830 756 690 524 421 355 204 -

Fig. 1. Infrared spectrum of I-(chloromethyl)-4-fluorobenzene between 3200 and 600 cm-r.

The ix. and Reman spectra of 1-(chloromethyl)-4-fluorobenzene

1609

Fig. 2. Infrared spectrum of l-(chIoromethyl)~4-~uorobenzene between 700 and 200 cm-*.

III

I

3000

I

I

I

I

2500

Ii

I

I

I500

I

I

I

I

I

lo00

F

I

I

I

I

III

500

Fig. 3. Raman spectrum of I-(chloromethyl)-4-fluorobenzene between 3300 and 200 cm-*.

r,,(s$)a’ at 732 cm-r or does not appear in the i.r. but in the Raman at -690 cm-l. The remaining skeletal modes y3,(y~~)a”/v,,(y~C)a” to be rtssigned are those associated with the out of plane bends of the fluo~ne/methylene C atom. Both bands should be (depola~zed)/rpol&~zed] on account of C,(a), C,,/G,[5] symmetry of the molecule. The weak bands at 3561204cm-l have been attributed to these modes [6] and there is no evidence against these assignments. The bands are polarized which favours G,[b] symmetry.

methylene stretch is expected to be depolarized on account of C,(a) or C,[b] symmetry whereas s, polarized band has been observed. The ~s(&H&a is found to absorb at 1445 orn-1 and the ~~s(wCH,)a’ at 1266 cm-r. The weak band at 1464 em-l is probably 2~&-4’). The vss(rCHs)a”and rss(pCH,)aW are more difEcult to trace, but we assume these modes to absorb at 1149 cmW1and at 756 cm-l as a shoulder of the strong us,, mode absorbing at 732 cm-l.

ikfethglenevibratiorrs

The remaining modes to be considered are Asia’, Y~,&%NI)cL’and vss(rCH&l)u” of which only ~sr could be located at 669 cm-l [S]. The v2s =cl F+% are either too weak to be observed or

The v~,(Y~CH&“ and ~s(~$Hs)a are easily looeted at 296512966 snd 2870/2870cm-l in the i.r./Raman spectrum of C&IF. The ~tis~et~e

W. A. SETH-PAUL and H. SEINO

1610

coincide

with

other fundamentals,

vs7 and yas with vea. However, vss absorbs at frequencies

e.g.

yZ6 with

it may also be that

<200 cm-l.

CONCLUSION On account for

vss and

molecule

of the depolarization

vs5-ves, one would

is of C,[b] symmetry.

the ratios observed v2s would

indicate

C,(a) symmetry. zed on account

Moreover,

that

the

On the other hand,

v2, should be depolari-

or C,[b] symmetry

a polarrzed band has been observed. although

whereas Therefore,

the data in this paper have been inter-

preted on the basis of C, symmetry,

the depolari-

zation

the molecule

measurements

indicate

is probably of C, symmetry.

REFERENCES

ratios observed

conclude

for v6-v 89Y10’ vn2~viny v20~v22and that the molecule agrees with

of C,(a)

Acknowledgements-We are grateful to Dr. P. A. J. JANSSEN and Mr. P. J. A. DEMOEN for their interest and cooperation duping the course of this work. We are also indebted to Mr. W. VAN LAERHOVEN for distillation and to Mr. A. VAN DE~TN for gas chromatographic analysis of the compound.

that

[l]

J. N. RAI and K. N. UPADHYA, h’pectrochim. Acta 22, 1427 (1966). M. HORAK, E. R. LIPPINCOTT and R. K. KHANNA. i2] Spectrochim. Acta 23A, 1111 (1967). [31 N. L. OWEN and R. E. HESTER, Spectrochina. Acta 25A, 343 (1969). 141J. H. S. G~~~~,Sp%trochim. Acta 20A, 1603 (1970). [51 M. A. SHASHIDHAR, K. S. RAO and E. S. JAYADEVAPPA, Spectrochik. Acta 26A, 2273 (1970). 161L. VERDONCK and G. P. VAN DER KELEN, Spectrochina. Acta 28A, 66 (1972). [71 J. H. S. GREEN, D. J. HARRISON, W. KYNASTON andD. W. SCOTT,8peCtrOchim. Acta26A, 1516 (1970). PI C. W. BIRD, Spectroch&. Acta 24A, 1666 (1968).