mass spectrometry of paraquat UV-ozonation products

Chemosphere, Vol.14, No.9, P r i n t e d in G r e a t B r i t a i n

pp

1181-1194,

1985

0 0 4 5 - 6 5 3 5 / 8 5 $ 3 . 0 0 + .OO 0 1 9 8 5 P e r g a m o n P r e s s Ltd.

GAS CHROMATOGRAPHY/MASS SPECTROMETRY OF PARAQUAT UV-OZONATION PRODUCTS

John M. Ruth,* Philip C. Kearney and Qiang zeng Pesticide Degradation Laboratory, Agricultural Environmental Quality Institute Beltsville Agricultural Research Center, ARS, USDA Beltsville, Maryland 20705

ABSTRACT The c h r o m a t o g r a p h i c and m a s s s p e c t r a l p r o p e r t i e s o f 13 compounds i s o l a t e d from t h e r e a c t i o n o f UV and o z o n e on p a r a q u a t a r e d e s c r i b e d . The p r o d u c t s w e r e e x t r a c t e d from t h e a c i d i f i e d r e a c t i o n m i x t u r e and c o n v e r t e d t o TMS d e r i v a t i v e s . The i d e n t i f i e d p r o d u c t s were t h e diTMS ester of oxalic acid (m/z 234), the TMS ester of 4-picolinic acid (m/z 195), the diTMS ester of succinic acid (m/z 262), the diTMS derivative of N-formylglycine, 4,4'-bipyridyl (m/z 156), the triTMS derivative of mallc acid (m/z 350), and the diTMS derivative of a hydroxy-4picolinic acid. Structural features and tentative identification of some of the remaining compounds are discussed. The most prominent peak on the chromatogram has a probable molecular ion at m/z 219, isomeric to the diTMS derivative of glycine. The structures presented suggest that demethylation, ring oxidation and fragmentation of one or both rings of the b ipyridinium dl-cation occur during UV-ozonation of paraquat.

INTRODUCTION Recently we reported on the combined use of UV and ozonation to fragment three widely used herbicides as a pretreatment step prior to soil disposal (I).

The ionic herbicide paraquat

(l,l'-dimethyl-4,4'-bipyridlnium dichloride) was found to degrade more slowly than either atrazine or 2,4-D.

More extensive studies with paraquat were undertaken to determine the

effect of concentration and photosensitization on the rates and products of UV-ozonation (2). Most product studies on paraquat have addressed the early quaternary ammonium compounds resulting from photochemical or metabolic reactions (3).

The first step in the chemical reduction of paraquat is the reversible addition of one electron to form a stable, water-soluble ion-radlcal of deep blue color (3-5).

Controlled

oxidation under alkaline conditions produced pyridone-ion and dipyridone structures retaining the methyl group on each nitrogen atom (3,6).

Irradiation of dilute solutions with UV light

of sufficient energy, in the presence of oxygen, gave two major products, the 4-carboxy-lmethylpyrldinium ion and methylamine (7,8). obtained instead.

In the absence of oxygen, polymeric products were

Microbiological degradation in solution was believed to have produced the

4-carboxy-l-methylpyridinium ion (9).

Microbiological degradation of that ion in soll yielded

1181

1182

carbon dioxide, formate, succinate, and methylamine (10-14).

The adsorption of paraquat by

soll minerals makes it unavailable for herbicidal action (3), but also retards its degradation (15), and the "storage" capacity of soils is limited (16).

The preliminary degradation

before soil disposal is then obviously desirable.

Organic chemical ozonations

are

normally done in nonaqueous solvents.

The primary ozonide

(l,2,3-trioxolane) undergoes rapid reaction by ring cleavage to carbonyl and carbonyl oxide (zwitterion) groups, leading to the ozonide (l,2,4-trioxolane) or other products (17-19). aqueous solutions, water becomes one of the reagents. OH radical is probably the most important. present,

In

Among oxidizing species generated, the

UV irradiation activates all absorbing species

including the ozone itself, the organic contaminants, and their intermediate oxida-

tion products.

The resulting set of reactions,

if allowed by time and other variables to go

to completion, eventually will yield CO2, H20 , SO 2-, etc. as the final products (20-25). 4 The objective of the present paper is to describe the gas chromatographic and mass spectral properties of several nonquaternary compounds derived from paraquat by UV-ozonation of a dilute aqueous solution.

MATERIALS AND METHODS

Sample Preparation

Details of the reaction conditions, concentrations,

and rates have been described (2).

Briefly, an aqueous solution containing 20 ppm of paraquat (99.8% pure) was irradiated with UV for 30 min in the presence of oxygen.

The reaction mixture was acidified with dilute HC1

to pH 2 and extracted three times with I L of ethylacetate. a rotary evaporator and then to dryness under nitrogen.

The extract volume was reduced in

Samples were resuspended in I00 uL of

purified pyridine and trlmethylsilyl derivatives prepared with I00 ~L bis(trimethylsilyl) fluoroacetamide (BSTFA) at room temperature for 30 min. achieved by gas chromatographic/mass

tri-

Separation and identification were

spectrometric analysis.

Instrumentat ion

The gas chromatography/mass

spectrometry (GC/MS) was done with a Finnigan Model 4021 system.

This system consists of a Finnigan Model 9610 gas chromatograph controlled separately by its own microprocessor;

a Model 4021 quadrupole mass spectrometer; and the Finnigan INCOS data

system, which controls the automatic repetitive scanning of the mass spectrometer, acquires the data, stores the data in a suitable form, and, under operator guidance, completes the data processing.

The data system includes a Data General Nova 3 computer; a Finnigan MS-IO

interface board, model 2010 interface box, scan receiver, detector preamplifier, and disk controller, which together handle scan control and data transfer operations; a CDC Model 9448 disk drive (32 Megabyte ODD); a Tektronix Model 4010 computer display terminal, a Printronix Model 150 printer; and Finnigan INCOS series 3.1 software release, MSDB Rev. 03.02.80.

1183

The column, manufactured

by J & W Scientific,

Inc., was a 30-meter

inside diameter 0.239 mm, coated with a 0.25 cM film of SE30. 20 psi gauge pressure. min at 90°C,

The oven temperature

processor

from there to 230°C st 5"C/min,

was asked to renew its "ready"

the mass spectrometric

and hold at 230"C.

signal.

and the filament, multiplier

comparisons

then depend upon the constancy

injection,

by difference.

When the signal appeared, After

1

The GC micro-

the GC program and

15 sec the sample was injected,

for the passage of the solvent peak, the ion source vent

was closed,

sample

injection technique was:

The sample for injection was

for measurement

data acquisition were started.

the high vacuum gauge was observed

The carrier gas was helium at

program for the Grob

drawn up into the glass barrel of a 5-¢L syringe

fused silica capillary with

and conversion dynode were turned on.

Retention

of the interval between system activation

and upon the reproducibility

of the temperature

time

and

curve.

RESULTS

The c h r o m a t o g r a m ( F i g u r e UV-ozonation products min t o 20 mln ( s c a n s the

introductory

1) o f t h e TMS d e r i v a t i v e s

shows f o u r r e l a t i v e l y 150-600,

section

p r o c e s s may be e x p e c t e d

interest, relative

large

a t 2 sec p e r s c a n )

a b o v e , an u n u s u a l l y to set

b e g i n s w i t h a more o r l e s s and f o r p r a c t i c a l

in t h e r e t e n t i o n

time range from 5

number o f o t h e r s .

p o w e r f u l and n o t v e r y s e l e c t i v e

analysis

purposes turns

As n o t e d

o u t t o be l i m i t e d

and t h e e x p e c t a t i o n

Its

description at the time of

by s u c h c o n s i d e r a t i o n s

of properties

J

~icj

6

9 12

3

?

10

11

/l

L. . . . . . i 2~

6:40

Figure

1.

i

13:2e

16:.~

as t h e

b a s e d upon i n d i c a t i o n s

Rtc x lO

in

degradation

of the major components p r e s e n t

L

I

peaks

and a l a r g e

(20 ppm in w a t e r )

up a c o m p l e x s y s t e m o f c o m p e t i n g r e a c t i o n s .

qualitative

abundances of products

of the 30-min p a r a q u a t

t

~:m

TIME

R e c o n s t r u c t e d I o n C u r r e n t C h r o m a t o g r a m f o r TMS D e r i v a t i v e s of Paraquat UV-Ozonation Products.

of

1184

relative molecular

size.

The present mixture conforms

portion of the chromatographic procedure,

the emergence

and some material

record (scans

to that general pattern.

I to 150)

of the pyridine-BSTFA

solvent peaks (ion source and multiplier

probably containing both the derivatives

of very volatile products.

The initial

is taken up with the Grob injection

of any solvent

impurities

off)

and those

The portion from scan 600 to scan 902 is likewise not of immediate

interest here, showing only indications

of very small chromatographic

peaks decreasing

to a

flat baseline.

The tallest peak (maximum one component relative

in scan 163), labeled

in ion profiles

intensities

across

are m/z 219(RI 1.6%), I00(0.7%),

I in Figure

its two scans,

95(3.7%),

204(28%), 86(I.5%),

147(I00%),

I17(0.9Z),

I02(0.7%),

45(5.0%).

The mass peak at m/z 219 probably represents

is found in the mass spectra of the ~MS derivatives and 147 are common

in the spectra of derivatives

or more TMS groups per molecule,

I, shows no evidence of more than

162 and 163.

73(26Z),

The important 133(3.0%),

66(16%),

the molecular

of hydroxy compounds.

of polyols

131(4.4Z),

59(6.2%), ion.

ions and their

52(1.9%),

and

The ion at m/z 73 Those of m/z 45

and other compounds

containing

two

where the two ~4S groups can be brought near each other (26).

The ion [(CR3)3SiOCR=CHSi(CR3)3 ]+ of mass 204 is sometimes if the molecular

weight

seen in the spectra of such compounds

sition or structure of the ion shown. two TMS groups are possible, derivatlzation

weight,

In a derivative

and the molecular

must have been 75.

the odd molecular

are then (case I) C3H9NO,

(sometimes

Possible compositions

(case II) C2H5NO2,

of an aromatic

none) for derivatization

ring.

There,

for

and the remainder of the

and (case Ill) CHNO 3.

molecule

Structures attractive

as

Those of case III have no more than one site

and are therefore

rejected.

resembles that of a dITMS derivative

for the low intensity at m/z 102, which

derivative.

product before

atom to account

for the underivatlzed

saturated open chains, not immediately

The mass spectrum of the unknown derivative except

weight 219, no more than

included one nitrogen

since three of them are not available,

covered by case I are completely products

of molecular

weight of the UV-ozonatlon

This must have

structure must add up to 61 mass units.

UV-ozonation

(26), but in the present case,

is 219, the 204 is just the (M - 15) ion and does not have the compo-

of glycine,

is the base peak in the spectrum of the glycine

the 102 ion is obtainable by cleavage of the molecular ÷

ion to give

(CH3)3Si-NH=CH 2 by the same process observed material.

That

in underivatized

below m/z 80 is very similar

are similarly c o m o n ,

evidence belonging

The spectrum

of hydroxy acids and dlols.

The peaks between m/z 80 and 146

and of such low intensity as to suggest the absence of any facile

Thus, the only characteristic

from the molecular

in an amine group.

to that of oxalic acid, and the same peaks may be seen in the

spectra of the TMS derivatives

cleavage.

amino acids, evidently not easy in the unknown

is, the nitrogen atom is probably not present

ion, undoubtedly

is largely negative

cleavage

indicated

from a trimethylsilyl

in nature.

Disregarding

to case II above were tabulated.

is the loss of a methyl

group,

optical

and the visible

isomerism,

Many can be excluded

radical

structural

98 structures

for one reason or another.

1185

Some have less than the required two active hydrogens.

Others, although likely to be stable

in the form of TMS derivatives, may not be obtainable in that form through the UV-ozonation procedure and subsequent treatment of the mixed products.

The best approach to an identifica-

tion is through the collection of the more promising candidates and the examination of their spectra, in most cases involving synthesis.

That will be undertaken as time and other

resources permit.

The small OC peak 2 (maximum in scan 168) contains the diTMS ester of oxalic acid.

The molec-

ular ion at m/z 234 does not appear either in scan 168 or in the spectrum of the DiS derivative of a reference standard.

In scan 168 the following fragment ions and corresponding

relative intensities were observed:

m/z 219(RI 5.2%), 190(7.1%), 175(0.9Z), 147(100Z),

133(2.7%), 131(2.4%), I02(3.6%), 73(I00%), 66(8.5%), 59(2.0%), 58(1.8Z), 52(2.2%) and 45(6.8%).

In the derivative of the authentic compound, the corresponding data are 219(2.9%),

190(4.8%), 175(0.9%),

147(58%), 133(2.5%), 131(1.9%), I02(I.1%), 73(I00%), 66(7.5%), 59(5.5%),

58(3.8%), 52(2.7%) and 45(12%).

The spectrum of the unknown shows some rise in concentration

in the ion source as the small, narrow GC peak moves through the source during scan 168, in comparison with the spectrum of the standard, minimized.

for which such concentration trends could be

The intensity of the m/z 147 ion is additionally influenced by the fact that it is

the principal background peak at this point, whose intensity will increase in the source as its rate of evacuation is decreased by the transitory rise of ion source pressure during the passage of the GC peak through the source, an effect demonstrated for the helium carrier gas itself (27).

The agreement

is not only very good under the circumstances, but in fact

fortuitously dependent upon the totally accidental relationship between GC peak rise and MS scan progression in the short period of time involved.

C h r o m a t o g r a p h i c peak 3 ( F i g u r e 2) a p p e a r s t o c o n t a i n two c o m p o n e n t s , e a c h of m o l e c u l a r w e i g h t 219.

Ions r e l a t i v e l y

Those o f s i g n i f i c a n t

i m p o r t a n t i n peak 3 ( a ) b u t not intensity

in 3(b) b u t n o t

Component 3 ( a ) b e g i n s in s c a n 196 b u t i s l a r g e l y essentially spectra,

i s c o n f i n e d t o s c a n 198.

single

ion p r o f i l e s

cannot,

in 3(b) a r e o f m/z 104, 116 and 188.

in 3 ( a ) a r e found a t m/z 117 and p o s s i b l y concentrated

in s c a n 197.

For two i s o m e r i c s t r u c t u r e s in t h e a b s e n c e o f r e f e r e n c e

Component 3(b)

having rather spectra

179.

similar

of the p u r i f i e d

com-

p o u n d s , d e c i d e t h e p r e s e n c e or a b s e n c e o f a s m a l l o v e r l a p o f t h e two c h r o m a t o g r a p h i c p e a k s . I t m u s t be remembered a t t h i s equal height,

require

two c o m p l e t e l y r e s o l v e d c h r o m a t o g r a p h i c p e a k s o f

o c c u p y i n g a d j a c e n t s c a n s , w i l l a p p e a r as a s i n g l e

A l a r g e enough i n c r e a s e duration)

point that

rectangular

peak on t h e g r a p h .

in s c a n s p e e d as e x p r e s s e d in s c a n s p e r s e c ( s h o r t e n i n g o f s c a n

would p e r m i t t h e g r a p h t o r e t u r n

to b a s e l i n e

a s h o r t e n i n g of the mass range s c a n n e d ,

b e t w e e n t h e two r e a l p e a k s b u t would

in k e e p i n g w i t h t h e

instrument's

characteristics.

The m a s s s p e c t r u m o f compound 3 ( a ) h a s i t s 188(13%),

174(8.8%),

66(9.9%),

59(5.[%)

3.5%), 2 0 4 ( 4 . 9 % ) ,

163(2.0%),

and 4 5 ( 6 . 6 % ) . 188(1.0%),

147(49%),

principal

i o n s a t m/z 219(RI 5.3%),

116(7.8%),

For compound 3 ( b ) ,

179(1.2%),

174(9.1%),

75(30%), 73(100%), 66(14%), 59(7.8%) and 45(10%).

104(10%),

204(11%),

100(12%), 75(22%), 73(100%),

t h e c o r r e s p o n d i n g d a t a a r e m/z 219(RI

163(3.1%),

147(61%),

I t m i g h t be a s k e d ,

117(9.3%),

I00(17%),

f o r an a l t e r n a t i v e

1186

IHTEH

I. 1~6S H,'Z 174

\

2

M Z 116

/?' / / " ,,"

//

//

•' f

194

196

6:28

6:32

F i g u r e 2.

interpretation,

decimal

fractional

graphic

peak,

redefined

a s a m i n o r component whose mass s p e c t r a l

mass v a l u e s

of the extension

the stronger

one,

the nature

concentration

alternative.

Detailed

scans,

single-ion

variability

profiles

across

to unfounded the chromato-

scans fall

the

first

the latter

two s c a n s and t h e m / z 117 in t h e t h i r d statistical

so n e a r t h e

integer

width of

in t h e m / z 274 t o 219 r a n g e and a

d r o p in t h e h i g h - m a s s end o f s c a n 198 d i d n o t s u p p o r t

fluctuations, values

that

scan are strong

and t h e d e c i m a l m a s s v a l u e s

rounding errors

in m a s s v a l u e s

out.

F i g u r e 2 from t h e m a p p i n g p r o g r a m shows t h r e e ion c u r r e n t

representing

the other.

planned

plot,

116 r e p r e s e n t i n g

Because the

evidence

single-ion

in c o n n e c t i o n w i t h p e a k l ,

profiles:

one o f t h e h y p o t h e t i c a l

interpretation

GC peak 4 (maximum i n s c a n 236, F i g u r e yielded

i n c l u d e m/z 188,

o f s u c h a weak c h r o m a t o g r a p h i c p e a k o v e r t h e t h r e e - s c a n of intensity

The m/z 116 in t h e

individual

syntheses

peaks

examination of the data with regard

from s i n g l e

e n o u g h t o be o u t o f t h e r a n g e o f l a r g e

the total

116 2~ 6:48 TIME

L98 6=36

t h e s w i t c h from m / z 116 in s c a n s 196 and 197 t o m / z 117 i n s c a n 198,

unlikelihood

in t h e

u

MAP P l o t s o f I o n P r o f i l e s f o r CC Peak 3, Showing Two M a j o r C o m p o n e n t s .

116 and 104 b u t n o t 204 o r 219.

are ruled

-- 174

~

w h e t h e r c o m p o n e n t 3 ( b ) c o u l d a l s o be t h e m a i n component i n s c a n s 196 and 197,

w i t h component 3 ( a )

possible

F"

further

m/z 174 w i t h t h e s h a p e o f c o m p o n e n t s , and 117

o f GC p e a k 3 s h o u l d be a s s i s t e d discussion

will

be p o s t p o n e d .

1 ) , when e x a m i n e d by means o f s i n g l e - i o n

for the presence of several

by t h e

profiles,

v e r y s m a l l GC p e a k s b e n e a t h t h e l a r g e one

1187

I NIF..H 40080. 1. M~6S --900

/ /

/ ~

/

/

'

'

"-~ '"~"

'

230 7:40

Figure 3.

(Figure 3).

I

//.. "~i\\

.~___J/i I

, fi.'Z 13@

\ /"

'

M+Z 147

130

ji

'

li z 180

RIC

I

I

]

235

[

[

]

248 8:80

7:5t3

SCAN TIME

MAP Plot of GC Peak 4 (4-Picolinic Acid TMS Ester), with Ion Profiles of Major Component and Minor Impurities.

In this example, some experiments with "background

subtraction"

schemes

involving

scans within the large peak succeeded

in providing a satisfactory

nent.

ion at m/z 195(4.2% RI) and a base peak at 180(I00%).

The spectrum shows a molecular

Other fragments of significant 75(4.9%),

intensity are:

73(6.8%), 51(15%) and 45(4.3%).

of the TMS ester of 4-picollnic 90(3.9%),

78(26%), 75(4.3%),

acid:

136(27%),

spectrum of the main compo-

106(41Z), 90(4.7%),

78(33%),

This spectrum is in excellent agreement with that

mlz 195(4.1% RI), 180(I00%),

136(24%),

I06(35%),

73(7.5%), 51(II%) and 45(4.1%).

GC peak 5 is that of the dITMS ester of succinic acid, with its maximum in scan 267. mass spectrum has a molecular 218(0.8%),

173(2.0%),

ion at m/z 262(0.2% RI) and fragment

172(3.5%),

75(14%), 73(47%), 56(3.6%),

147(100%),

133(2.1%),

55(6.3%) and 45(2.7%).

the succlnic acid standard has m/z 262(0.3%), 147(I00%), and

133(2.0%),

129(4.7%),

ion peaks at 247(16.7%), 129(3.4%),

I16(1.7%),

The mass spectrum of the diTMS ester of

247(16%),

I16(0.6%),

218(0.8%),

173(1.4%),

172(2.7%),

75(20%), 73(33%), 56(1.2%),

55(2.4%)

45(0.8%).

Chromatographic 298.

131(0.8%),

131(0.9%),

The

peak 6, containing the diTMS derivative of N-formylglycine,

In scan 300, the sample concentration

begins in scan

is high as the scan begins with the low-mass peaks

but falls rather rapidly before the high-mass peaks are recorded.

Detailed examination of the

three scans indicates that a small amount of a second constituent

characterized by its m/z 144

1188

8752

~

,

•

t

x\

299

~

230 144.04 i 0.50

\\ "x

299

S

""\ •

~BI

7 301

'~

•

:t (L 50

I

299

////~

INTEN ~00. I. ~SS ~9~0

73.02 0.50

t

174.05 0.5@

299

15 ±

0.50 M-'Z 73

299

22 246.07 ± 0.50

x

/

1897g

.

_

~

.

M/Z 144

.

/

~

1

4

4

.~i-298 9:56

'

3~2 5CAN

3~0 10:80

I

I@:04 TIME

'

I

9:56

and 246 i o n s i s p r e s e n t

summing t h e

identified,

three

(b)

in s c a n s 298 and 299, b u t n o t

in s c a n 300 ( F i g u r e 4 ) .

t h r o u g h s c a n 300, w h i c h i n t e r f e r e s

v a l u e s by s u b t r a c t i o n s .

and a r e e a s i l y

Since the the best

with efforts

i o n s from t h e m i n o r c o n s t i t u e n t

s c a n s and t h e n r e j e c t i n g

the small peaks a s s o c i a t e d 171(0.08%),

218(0.1%),

o f t h e m i n o r o n e , and t h e one t h a t i t s m / z 246 peak a d j a c e n t

prompted a c a r e f u l

to the 247(m ole c ula r

232(5.4%),

204(7.0%),

188(1.5%),

157(0.8%),

147(32%),

117(1.3%),

116(0.7%),

102(9.9%),

100(1.0%),

75(24%),

The c o r r e s p o n d i n g

peaks of a s ta nda rd

only with the minor

preparation

some

the most

examination of

ion) of the o t h e r .

133(1.0%), 74(7.2%),

and p o s s i b l y

In t h e b e g i n n i n g ,

s p e c t r u m o f t h e a b u n d a n t component o f GC p e a k 6 shows t h e m o l e c u l a r

and 4 5 ( 6 . 7 % ) .

good i n t e n -

a r e o f low i n t e n s i t y

246(0.2%),

even weaker ones above the mass range of the abundant component. annoyiDg f e a t u r e

The c o n c e n t r a -

to obtain

s p e c t r u m o f t h e m a i n c o m p o n e n t a p p e a r s t o be o b t a i n e d by

c o m p o n e n t , w h i c h a r e a t m/z 144(RI 1.8%),

the presence of

5CAN

10:84 TIME

Plots for GC Peak 6 (N-Formylglycine DiTMS Derivative): (a) From the Chromatogram (CHRO) Program; (b) From the MAP Program.

tion drop is appreciable sity

?3

302

10:~

(a) Figure 4.

'

~

it,

was

The mass

ion a t m/z 247(RI 0 . 1 % ) ,

132(1.1%),

73(100%),

130(20%),

59(2.2%),

were 2 4 7 ( 0 . 4 % ) ,

47(2.1%)

232(7.4%),

1189

204(11%), 188(3.0%), 116(2.1%),

157(1.4%),

102(9.2%),

133(1.6%),

147(34%),

132(2.1%),

130(19%),

100(3.8%), 75(52%), 74(8.8%), 73(100%), 59(3.1%), 47(3.0%) and 45(9.8%).

The p r i n c i p a l component o f GC peak 7, o c c u p y i n g s c a n s 376 and 377,

is 4 , 4 ' - b i p y r i d y l .

components on each s i d e a r e l a r g e l y in s c a n s 375 and 378, and t h e i r central

component a r e removed by s u b t r a c t i n g

s c a n s 376 and 377. 155(51%), 51(12%)

128(7.0%),

and 50(7.2%).

155(49%),

spectrum

128(9.3%),

101(2.0%),

of the reference

I02(5.9%),

of GC peak 8 (maximum

side by subtracting

justing

the background

disappears.

101(3.2%),

in scan 386)

a portion

standard

78(3.3%),

of the averaged

multiplication

76(5.8%),

has m/z

77(1.9%),

The result

is m/z 275(R1

until

63(2.2%),

156(100%), 76(5.4%),

1.8%),

260(25%),

156(5.0%),

147(55%),

142(4.8%),

I13(4.0%),

I02(2.2%),

88(2.0%),

86(2.2%),

59(3.0%),

58(2.8%),

56(3.0%),

molecular

its mode of production

The tentative undergone

hypothesis

it must be recalled upon sufficient

ities.

The superscripts molecule,

63(2.6%),

as to ensure

atoms

are the labels

identifying

the carbon

C5

- C4 - C 3 - C 2 - N

(C)

C4

- C 3 - C2 - N

- CM

(D)

C4

- C3 - C2 - N

- C6

(E)

C3

- C2 - N

- C6 - C5

(F)

C3

- C2 - N

- C6

(A) through

keeping

and basing

the scheme

are overlooked.

II, one from category

cleavage),

what

of the product origins

formula

fragments

in these cases

(C).

in mind

has

rearrange

of their

itself not

to C-substituted

are possible

in the parent

group:

an orderly

upon structural

Also

the possibil-

positions

the requirement

Structure

of

of the fragment.

from the N-methyl

(F), one may then adopt

compounds,

68(36%),

pattern.

pyridines

C 4' - C 4 - C 3 - C 2 - N

for inquiring

look like simple

that N-alkyl

(B)

by TMS groups,

The empirical

skeletal

(A)

that no possibilities

method

skeleton

just

129(2.6%),

73(90%),

both with the chemistry

fragmentation

on

186(17%),

so that the list below does not exhaust

on the carbon the label M

(A) or (B), and structure systematic

(28),

of the imaginable

replaceable

spectral

at this point

W ithin each of the categories classification

and 45(6.1%).

in scan 385)

130(3.0%),

74(11%),

peaks

385 and 387) and ad-

188(6.8%),

131(1.2%), 75(25%),

a list of six possible

heating

with

232(2.0%),

compatible

that the carbon-nitrogen yields

isomers

paraquat

47(I.[%)

275, appears

and with the mass

rearrangement

However,

55(12%),

weight

(scans

of smaller

the m/z 84 (maximum

158(100%),

C4H3NO4(TMS)2,

background

factor

I14(1.3%),

will

77(2.5%),

is freed of the overlaps

173(1.0%),

atoms

component has m/z 156(RI 100%),

78(3.8%),

and 50(5.0%).

The spectrum either

The mass

129(7.6%),

51(6.7%)

102(4.5%),

Minor

small o v e r l a p s w i t h t h e

t h o s e two s c a n s as background from t h e sum of

The mass s p e c t r u m o f t h e 4 , 4 ' - b i p y r i d y l

129(5.1%),

117(3.1%),

scheme

features

I is an example

illustrated by simple

from the molecular

with

of

of two hydrogen in such a way

from category

I and II is a

cleavage

(or by what

ion, avoiding

for the

1190

731

1171 1451

891 I

I

,

,:

,

I

1591 18r I

I

. ° . ° ,

I

.°,

IT, l

l

Ill

l U l

I

I

I

2021

I

t31 89~ 11 h 14-51 I?31 20~

I

I

I

I l

,

,

I

I

I

IT3

1~02 I~s6 1158 1~30 1~02 IT3

.

l ~ll I Ill

.

I

I

I

1~6 188

I

I

l

l

l

l I I

I

I I

t I

I I

I moment any preconceived

I

TMS?O-~C -+-C-~ C--~ N ~-TMS

TMS~ O ~ C -~-C~ C Hz-+-C~- NH -+TMS I I I I 1 I 1202 Ilae I1s8 1~30

I

I

II

ideas in favor of or against any of them.

To select one example

from among many, the investigator will note that all or most of the more intense ion peaks are common to a number of possible structures, and eventually will find himself looking again at m/z 102 (RI 2.2%).

If cleaved from the molecular ion, it may have the composition equivalent

to CH3-N-~MS.

If similarly derived from the M-15, or from the 117, it may be

CO2-Si(CH3) 2.

It may have arrived by other pathways,

including rearrangement processes.

Clearly, the final stage in the identification of the compound will involve the synthesis and examination of candidate compounds.

GC peak 9 has i t s maximum at scan 396. 0.06%), 335(2.6%),

307(0.6%),

Mass v a l u e s and r e l a t i v e

306(0.3%), 265(0.7%),

189(5.7%),

175(2.1%),

191(3.1%),

190(4.3%),

101(2.3%),

75(11%), 73(100%), 59(0.9%), 55(3.6%) and 45(2.6%).

147(55%),

triTMS d e r i v a t i v e of m a l i c a c i d are 350(0.1%), 263(1.3%), 245(18%), 233(43%), 217(4.2%), 117(2.8%),

133(4.2%),

are m/z 350(RI

131(0.5%),

117(4.1%),

The c o r r e s p o n d i n g d a t a for the

335(10%), 307(3.0%),

191(6.1%),

101(5.4%),

intensities

263(0.5%), 245(11%), 233(26%), 217(0.9%),

306(3.4%),

190(11%), 189(9.0%),

265(2.5%),

]75(5.7%),

147(50%),

133(7.4%),

131(2.2%),

75(13%), 73(100%), 59(2.0%), 55(5.0%) and

45(4.7%).

The differences in relative intensities between the two spectra correspond com-

pletely to the usual patterns of imperfections in GC/MS data.

The principal component of GC peak I0 (maximum in scan 427) yielded the following mass spectrum:

molecular ion at m/z 283(RI 10%), 268(100%), 196(1.1%), 194(0.6%),

166(1.4%),

165(8.9%), 151(0.5%), 147(4.5%), 127(7.0%), 116(0.4%), I00(0.4%), 96(0.5%), 77(0.5%), 75(6.0%), 73(31%),

66(0.3%), 59(0.5%), 58(0.4%) and 45(1.5%).

three available isomers, 2-hydroxy-3-picolinic 3-hydroxy-2-picollnic

The diTMS derivatives of the

acid, 6-hydroxy-3-picolinic

acid, all give the base peak at m/z 268.

acid and

The molecular ion at m/z 283

is always present but varies widely in relative intensity from one isomer to another. pattern of the relatively small peaks below m/z 268 is also quite variable. product would be expected to be either 2-hydroxy-4-picollnic

The

The UV-ozonatlon

acid or 3-hydroxy-4-picolinic

acid, depending upon the nature of the reaction producing it.

Neither isomer is currently

available for comparison.

The mass spectrum of the main component of chromatographic peak II has m/z 225 (RI 51%), 210(I00%), 182(4.7%), 166(14%), 147(15%), 138(4.1%), 136(16%),

I08(18%), I05(1.4%), 91(1.4%),

80(2.0%), 79(1.8%), 75(23%), 73(47%), 67(1.5%), 59(1.2%), 55(I.1%), 52(0.8%), 47(1.2%) and 45(5.0%).

Consideration of possible compositions to account for a molecular weight of 225

1191

r.7o C=O I

C=O I

OTMS

OTMS

III

IV

suggests such structures as III and IV.

The extensive and complex chemistry of the pyri-

dines was collected and reviewed by Klingsberg 429) in four volumes.

Four supplementary

volumes by Abramovitch (30) reflected the great interest in and rapid growth of the subject, and that activity continues.

Although the oxo- forms with intact rings (III and IV) give a

useful picture of the extent of oxidation involved, they are not intended to limit the consideration of alternative structures unless confirmed by synthesis.

Other than the usual

m/z 73, 75, 147, and 210 (H minus methyl), the peaks to be explained are the m/z 182, 166, 136, and

108.

If the fragmentation is dominated by the presence of the carboxyl group, the

m/z 136 is equivalent to the loss of the TMSO group, and the 108 to the loss of CO-O-TMS. Decarboxylation of the m/z 210 ion would give the m/z 166. tion processes need to be considered.

Alternatively,

ring fragmenta-

Loss of CO from the 210, a common process of qulnoid

structures, would give the small peak at 182.

The mass spectrum from chromatographic peak 12 ends with m/z 377(RI 33%). significant

The other ions of

intensity are at m/z 30243.2%), 259(3.3%), 231(1.7%), 217(17%), 215(1.7%),

204(2.5%), 185420%), 18447.6), 169(1.2%),

147(81%), 141(I.0%), 133(4.0%), 12942.6%),

116(1.5%), 99(I.0%), 9543.1%), 75(25%), 73(100%), 69(5.0%), 59(0.7%), 55(8.8%), 47(0.7%) and 4543.9%).

A likely molecular weight is 392.

rearrangements

in the fragmentation of such structures (31), and of the number and variety of

In view of the known complexity of

structures coneeivablej one of the types V through VIII or one with a ring opened serves to start the discussion.

The composition -CO-C(TMSO)ffiN-CO-CH<

TMSO.,~/

and the same plus another H easily

H TMSO~I

O

o; )o

0

I

~"OTMS

TMSO

O

O

OTMS

H

V

VI

VII

VIII

1192

account

for the two strong peaks at m/z 184 and 185.

carbon atom in position 4, with or without

m/z

peak at

to all of a ring except the

atom.

Looking at the strong

217, the observer may begin in the usual way by asking what parts of the molecule

are missing

from that

ion.

It may or may not be coincidence

that of the usual 247 ion of M S mass of a CO unit. helpful.

That amounts

the extra hydrogen

derivatives,

The determination

Further discussion

of peaks

which

that the missing mass

in that case bears the charge,

of ionic composition

by mass measurement

11 and 12 has been deferred

is equal to plus the

would have been

in anticipation

of

syntheses.

Gas chromatographic Table

I.

retention data for the 12 peaks discussed

In six cases, the identified

comparison

and were used at various

were nominally centrations

than long ones appeared

I.

Comparison

short retention

Under the circumstances,

the agreement

conditions

times more is rather good

of CC retention.

Peak Position UV-O 3 Mixture

( I n Scan Numbers) a

Peak Center

Standard

UV-O 3 Mixture

168

162

232

Average

Standard

UV-O 3 Mixture

Standard

168

168

168

165

227

234

233

233

230

I.

Oxalic acid d iTMS ester

2.

4-Picolinic TMS ester

3.

Succ i n i c a c i d diTHS e s t e r

265

264

266

270

266

267

4.

N-Formylglycine diTMS d e r i v a t i v e

298

302

299

309

298

306

5.

4,4'-Bipyridyl

376

375

376

383

376

379

6.

Malic acid triqMS d e r i v a t i v e

395

393

396

398

396

396

7.

Hydroxy-4plcol inic acid diTMS d e r i v a t l y e

426

---

427

---

426

aThe d u r a t i o n

acid

of each scan in the rep e titive

s e q u e n c e was 2 s e c o n d s .

in for

Sample con-

to that from the mass spectral data.

of measures

Compound

Chromatographi~

already discussed.

and one of the factors affecting

Leading Edge Peak Number

as synthetic materials

times to obtain mass spectra.

to be involved.

and lends further confirmation

above have been collected

were available

the same, subject to the general reservations

varied noticeably,

Table

compounds

1193

The compounds identified range from products still possessing both rings to single-rlng structures to still smaller ring fragments.

Materials of relatively complex structure, such

as those in GC peaks II and 12, may tentatively be regarded as intermediate forms awaiting further degradation, whose remaining concentration should be subject to adjustment by alterations in irradiation time or other conditions. in the system used.

Those conditions then remain to be evaluated

The presence of succinic and malic acids was noted with some particular

interest for further consideration in a future report.

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T u c k e r , B.V.

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1194

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