NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

311.05-11-3110561 April 28, 1971 10 578

Progress Report

on CONFIRMATION OF THE STRUCTURE OF PREVIOUSLY REPORTED

TERTIARY AROMATIC AMINE ACCELERATORS WITH

MOLECULAR WEIGHTS ABOVE 400

H. Argentar* and R. L. Bowen**

* Research Associate American Dental Association

Research Unit at the National Bureau of Standards,

Washington, D. C. 20234.

** Associate Director American Dental Association

Research Unit at the National Bureau of Standards,

Washington, D. C. 20234.

This investigation was supported in part by Research Grant DE02494-03

to the American Dental Association from the National Institute of Dental

Research and is part of the dental research program conducted by the

National Bureau of Standards in cooperation with the American Dental

Association; the Dental Research Division of the United States Army

Medical Research and Development Command; the Dental Sciences

Division of the School of Aerospace Medicine, USAF; the National

Institute of Dental Research; and the Veterans Administration.

IMPORTANT NOTICE NATIONAL BUREAU OF STAH

for use within the Government. Be and review. For this reason, the p whole or in part, is not authorize Bureau of Standards, Washington,

the Report has been specitically pr

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

accounting documents intended

bjected to additional evaluation

sting of this Report, either in Office of the Director, National

:he Government agency for which

ies for its own use. <NBS>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
' ;

. -

.

-

>,r.

‘
Confirmation of the Structure of PreviouslyReported Tertiary Aromatic Amine

Accelerators with Molecular Weights Above 400

In a previous report1

, the syntheses and accelerating

abilities of a number of novel aromatic amine accelerators (Fig. 1)

were presented. In this report, the confirmation of the

structure of these compounds by elemental and nuclear magnetic

resonance spectroscopic analyses are discussed.

ELEMENTAL ANALYSES . -The results of the elemental analyses are

presented in Table 1 and are reasonably consistent with the

chemical formulas shown.

In the case of PBX, the predicted elemental analysis

depends on the degree of polymerization (i.e., "n")

However, "n" could not be predicted accurately from the ratio

of the starting materials used, since the exact epoxy

equivalent weight, the extent of fractionation due to the

treatment of the product, and other factors (such as epoxide

homopolymerization) were not known. Therefore, "n" was

estimated from the elemental and NMR spectroscopic analyses.

To estimate ,f n" from CHN data, the following approach was

used:

The calculated C,H,N analyses for 3,5-xylidine

are 79.29% C, 9.15% H, and 11.56% N; for the

diglycidyl ether of bis-phenol A, 74.09% C,

7.11% H, and 0% N. The found values for these

elements were 75.7% C, 8.1% H, and 2.4% N.
These values were arranged into the following simultaneous

equations

79.29 x + 74.09 (1-x) = 75.7, 'Vo c

9.15 x + 7 . 11 (1-x) = 8.1, ‘Yo H

11.56 X = 2.4, ‘& N

The first equation is the carbon balance 2

; the second,

the hydrogen balance; the third, the nitrogen balance; x is

the weight fraction of 3, 5-xylidine.

Rearranging, these equations become respectively:

1.61 = 5.20 x

0.99 = 20.4 x

2.4 = 11.56 x

Since the values (Y.) on the left-hand side of the i

equations contain all the experimental error and those

(Z^x) on the right contain none, these equations are an

example of the general case, Y. = Z^x, where Y^ is the

measured value and Z^ the coefficient. The least square

solution for x is 3 ' 4

: ^iZ

x X =

TZ. 2

1

Solving, x = 0.2313, the weight fraction of the 3, 5-xylidine

segments. Based on this value, the difference between calculated and found values for the elemental analysis is 0.5%

or less. Converting to mole fractions there are about 1.183

moles bisphenol segment per mole of xylidine segment, indicating

a degree of polymerization of about 5.5; i.e.. n = 1/(1.183-1)
3

NMR SPECTROSCOPIC ANALYSES. -To confirm the structures of the

synthesized amines, the proton magnetic resonance spectra of

the amines in a suitable solvent were obtained using a Varian

A-60 spectrometer run at 60 MHz with tetramethylsilane as

the external reference*.

With the exception of the high- and low-melting BTX,

each amine was analyzed once. After each spectrum was obtained,

electronic integration of the spectrum to obtain the intensities of the various peaks was performed at least twice. The

heights of the steps of the integration line were measured

with a metric rule in centimeters.

The intensities measured from the integration lines were

converted to relative intensities by assuming that the area

of the benzylic methyl peak is proportional to the number of

benzylic hydrogen atoms in the molecule and by multiplying

each of the other intensities by the same proportionality

factor. Predicted relative intensities were obtained from

the structural formulas of the molecule. Assignments were

based on published spectra

5

. The results of the NMR analyses are given in Table 4, based

on spectra such as the one shown in Figure 2. They are consistent with the depicted structural formulas.

* The spectra were obtained by R. A. Thompson and Dr. R. B.

Johannesen of the National Bureau of Standards.
4

To obtain an estimate of the degree of polymerization

(

,r n" ) of PBX by an independent method, calculations, similar

to those used with elemental analysis data, were made using

the NMR data. Thus, if R is defined as the moles of bisphenol

segment per mole of 3,5-xylidine segment, and if I is the

intensity for protons of a given 6, then, in theory, * = cm 3

RIch S3, where ^ * refers to the methyl groups of the bisphenol

segment and ot_ refers to the benzylic methyl groups (on cm 3

the xylidine ring)

I = 10 RT aliphatic 6 CH 3

aromatic

and

8 ri 3

6 CH, ' 6 CH

The coefficients were taken to be the ratio of the

number of protons of a given type to that of the benzylic

protons, assuming a 1:1 addition of the diglycidyl ether of

bisphenol A and the amine, and also that no secondary amine

8

was present. For example, in the last equation, F is the

ratio of the number of aromatic protons in the bisphenol

3

segment to the benzylic protons? 6 is the ratio of aromatic

protons in the xylidine ring to benzylic protons. Substituting the experimental values in the above equations and

solving as before, R = 1.27 moles bisphenol segment per mole

of amine segment. This corresponds to a polymer with " n"

about 3.7. The predicted relative intensities were calculated

by using the two values of R in the above equation and six

for I CH 3

*
5

The foregoing two independent estimates of " n" for

the polymeric amine accelerator PBX suggest that its

average value is about 4 to 5 with corresponding molecular

weights of about 2,200 and 2.600, respectively.

With regard to the elemental analysis of BMX, using a

similar approach, namely, the least squares method for determining the weight proportions in a combination of two

materials, a good agreement (within 0.1%) between calculated

and found values is obtained if the excess glycidyl methacrylate

used (and remaining in the product) is assumed to have hydrated

to glyceryl methacrylate. Based on the least squares method,

it then constitutes 3.7% of the final product. Utilizing

NMR data, the glyceryl methacrylate constitutes 2.9% of the

product
6

References

} . Bowen, R. L. and Argentar, H. Tertiary Aromatic Amine

Accelerators with Molecular Weights Above 400. NBS

Report 10 277 (1970)

2

. Hougen, 0. A. and Watson, K. M. : Chemical Process

Principles, Part I, Material and Energy Balances . New York, John Wiley & Sons, Inc. 1943, pp. 167-176

3

. Natrella, M. G.: Experimental Statistics, NBS Handbook

91, Washington, D. C., U. S. Government Printing Office,

1963 (5 - 24)

4

. Hoel, P. G.: Introduction to Mathematical Statistics

(3rd) . New York, John Wiley & Sons, Inc. 1962, pp.

169-172.

5

. Bhacca, N. S., Johnson, L. F. and Shoolery, j. N. (eds)

NMR Spectra Catalog , Palo Alto, California, Varian

Associates, 1962.
XoII o- 0=0o Xo

iToo

0=0

o-o

II * o xMX

0=6 6=o i • X

Q_

00 ooMXO A

xoox I Xooo Xo

GO

m i) IOOOI X

00

Q_

AT rt xooox

CDCDp

Cn0

TJ0

,c

EhC LO 0H O

-P -P >i fd •H

.p -p w 3 0 O > £ c 0 H

4-4o00•—i 2£po

4-1

m

•H

-pc

•H p

TJ O 0 44 N

•H *• 0 £ 0

r£ *

•P C c o

>1 - H 0 -P0

U)

N P -H O P

-P 0

-H 1 o

i—I ro c p >i

4H 0 0H x P H 0 o 3 0ft

Cn

U

xO X •H

U 4-1 Cl Pm 0 0
.o o

o

«

CD <

(?)

Wdd
CN0

P

G

tn

•r4 ft

0

0 G 0 1 G 0 U rG

rd P G 0

^-s G G 0 •H H 0 44 —

<o 0 0 P G G rG 0 1 0 0 T5 0 < 0 P 44 S 0) iH 0 4-t 4J 0 G P

ft P 0 P 0 >1 0 G 0 4-4 0

ft rd P rH • P 44 44 0 rQ

o <i) ft •H ft P

(l) •H G g i—p G 0 »d CO p G -P G 0 0 0 £ 0 •H G 44 G

EH 0 0 G p 0 G rd 0

G >i P -p rG 44 PQ rH 0

ir>G 0 0 •H 0 * ftrG

• rd p G rQ 0 44 X g rd X P G iH • •H G

u (1) 0 0 0 •H 4-> 0 0

PQ G G *d G p Td 0 H 44 0 •H G 0 0 0 •H rG 44 4H G g rd rG •H G g 0 ft 0 1

1 0 0 p -P 0 •H 0 •H P rd P 0 % P 0 p rH tr> G

G ft-P 0 4H 0 ft ft 0 rd 0 0

0 0 G 0 G v— •H 44 •H

•H CnTJ 0 -P tn g G 44

-p G G 0 rd irs G P u •H P

44 M-i 44

tr>-H G "d H

G o

-p 0

0

<DP

0

0

G

o

•PG

•H0

O

ftG

o

0

G

-p44O

p

ft

0G

G

H O

£ 44 O

N G ^0 O

cn

o

p

a)

<uc

0

>144 rP

0

G g

O 4-) O *H 2

•H

rH a; >1 p

n 0

G

0 Q G

o

ft

o

p

ft

Td H

G

^

0

o

0G <D

I rd ft 44 0 •H 0 ft & G a. £ G •H 0 0 0 tn >1

0 0 0 G G 1—

'

p • •H 44

1—

ft CO •H 0 >1 oO G p 0 0)

CO 0 0 •P G — 0 44 P G G G

0 0 G •H 44 44 s •H G G 0 •H

rG P E-* > •H 0 ft 44 0 0 0 0 0

44 P CO P ft 0 > 0 ftG 44 0 0 0 ro 0 rH ft 44 P

4-! 0 • G ft P 0 •H 0 0 G 0

0 CO 44 44 44 0 0 G 0

0

r40

G 0

rd G

(1) G

G

H

CD -P G

O -H P £

rd P 0 G ft ** £ P G G ft 44

44 0 •H 0 0 0 0 * 0

0 0 0 0 1 44 0 0 g

0 0 0 •H G G 0 £ 0 -H •H 0 0

ft 0 ftG G G G 0 4-i G P G

0 0 •H 0 tji 1—

0 •H 0 G 0

•r4 G 0 G ft •H G rH g 0 G

0 0 G G g 0 0 0 ft 0 0 0

S* rQ 0 0 •H 0 0 G 0 p P ft P

S3 rd ftnd 2 0 0 G ft 0 0 0 ft
10

TABLE 1

ELEMENTAL ANALYSIS OF TERTIARY AROMATIC AMINES

Compound

c

Calculated* %

H N Cl c

Found*

H N

%

Cl

BPX 73 .4 6.4 8.0 72 .8 6.4 7.9 —

High

melting

BOX

63.7 6.0 2.9 14.5 63.6 6.0 2.9 14.5

Lowmelting

BCX

63.7 6.0 2.9 14.5 64 .

6.2 2.9 14 5

Highmelting

BTX

74.8 7.9 3.1 7 5.2 7.9 3 .

—

I.OV7-

me It ing

BTX

74.8 7.9 3.1 7 5.1 7.9 3.2 —

BMX 6 5.2 7.7 3 .

64 . / 7.8 3 .

—

PBX

(n = 5.5)

75.3 7.6 2,7 7 5.7 8.1 2 .

—
11

TABLE 2

NMR CHEMICAL SHIFTS e INTENSITIES FOUND AND

* THE r: THOSE p;

ELAT I VE

REDICTEDt

Compound Proton Assignment

Aromatic Vinyl Aliphatic Methy 1

7.76 m* 4.71 m 2.20s

(7.9; 8 )

t

(3.7; 4) (6; 6)

BPX $ 6.27 s 3.28 m

[5% in CDC1 S ] (2.8; 3) (3.5; 4)

1.67 ia (7.5; 8)

BCX, high melting

[20% in aqueous

90% formic acid]

6.67-7.43 m

(12.3; 11)

4.07 bs 2.31 s (10.1; 10) (6; 6)

BCX* low melting

[20% in aqueous

90% formic acid]

6.70-7.40 m

( 11 . 8 ; 11 ) 4.07 bs 2.26 s (9.5; 10) (6; 6)

BTX- high melting

[20% in aqueous

90% formic acid

6.58-7.35 m

( 11 . 2 ; 11 )

BTX, low melting

[20% in aqueous

90% formic acid]

6.62-7.18 m

(10.9; 11)

3.99 s 2.2 5 s

( 9 . 6 ; 10 ) ( 6 ; 6 )

2.09 s

( 6 ; 6 )

2.12 s

( 6 ; 6 )

1.98 s

( 6 ; 6 )

3.88 bd

(10.5; 10)
TABLE 2 (Continued)

Compound

BMX

[50% in CFsCOgH]

Aromatic

7.31 s (2.6? 3)

6.30-7.08 m

PBX [n = 3.7? 20% (12.5? 13.9)

in aqueous 90%

formic acid]

i

Proton Assignment

Vi ny 1 A1 iphatic Methy

I

6.2 5 s (1.7? 2)

5.77 s

( 2 . 1 ? 2 ) 3.78 bs 2.00 s (13.4? 12.7) (6? 6),

1.2 5 s

4.09 bs 2.41 el

4.41 bs (6? 6)

‘ (10.5? 10)

1.95 s"

( 6 . 2 ? 6-

(7.3

* In PPM (6) units relative to external reference compound t tetramethy Isilane . The letters after the 6 values indicate

the following: m, mu It ip let (a series of several overlapping

peaks)? s, singlet? bs, broad singlet, and bd, broad doublet.

t The first number in parentheses is the peak intensity found

(relative to benzylic methyl protons) and the second is that

predicted for a given proton based on the molecular formula.

i Methyl protons include aliphatic, benzylic and methacrylate.

^Internal tetramethy Isilane used as standard.