23 июня, 2015 
Malyar Gutmann [32] proposed a two-parameter equation for the estimation of AHAB:
-AHAB(kcal/mol) = (4)
where AN is the acceptor number of the acidic species and DN the donor number of the basic species. DN was defined as the negative of the enthalpy of formation of the
|
Polymers |
Ca |
Ea |
Cb |
Eb |
Method |
Ref. |
|
CPVC |
_ |
3 |
IR |
27 |
||
|
0.36 |
2.70 |
IR |
38 |
|||
|
PVB |
_ |
4 |
IR |
27 |
||
|
Phenoxy resin |
0.24 |
1.53 |
IR |
44 |
||
|
Epoxy resin |
0.29 |
1.72 |
NMR |
13 |
||
|
PVdF |
0.7 |
1.8 |
IR |
45 |
||
|
PMMA |
1.18 |
0.59 |
IR |
44 |
||
|
0.96 |
0.68 |
IR |
27 |
|||
|
PEO |
5.64 |
0.77 |
IR |
44 |
||
|
PPyCl |
0.27 |
4.17 |
0.45 |
1.09 |
IGC |
40 |
|
PPyTS |
0.27 |
4.35 |
24.5 |
—0.36 |
IGC |
41 |
|
PPO |
9.5 |
^ 0 |
XPS/IR |
43 |
||
|
PP-N2 |
0.32 |
1.46 |
XPS |
46 |
||
|
PP-NH3 |
0.91 |
1.65 |
XPS |
46 |
||
|
Fillers |
||||||
|
SiO2 |
1.14 |
4.39 |
MC/IR |
37 |
||
|
TiO2 |
1.02 |
5.67 |
MC |
37 |
||
|
a-Fe2O3 |
0.8 |
4.50 |
MC |
47 |
||
|
1.1 |
0.50-1.0 |
MC |
48 |
|||
|
K-Fe2O3 |
0.79 |
5.4 |
MC/IR |
38 |
||
|
E glass |
0.02 |
0.15 |
0.39 |
0.2 |
MC |
37 |
|
Glass beads |
0.70 |
6.0 |
IGC |
42 |
||
|
APS-treated glass |
1.60 |
0.62 |
IGC |
42 |
|
CPVC, chlorinated poly(vinyl chloride); PVB, poly(vinyl butyral); PVdF, poly(vinyl difluoride); PMMA, poly(methyl methacrylate); PEO, poly(ethylene oxide); PPyCl, chloride-doped polypyrrole; PPyTS, tosylate — doped polypyrrole; PPO, poly(phenylene oxide); PP-N2, nitrogen plasma-treated polypropylene; PP-NH3, ammonia plasma-treated polypropylene; MC, microcalorimetry; APS, aminopropyltriethoxysilane. |
acid-base adduct between the base under investigation and a reference Lewis acid, antimony pentachloride (SbCl5) in 1,2-dichloroethane (inert solvent):
DN = —AH (SbCl5:base) (5)
AN, the acceptor number of Lewis acids, was defined as the relative 31P NMR shift obtained when triethylphosphine oxide (Et3PO) was dissolved in the candidate acid. The scale was normalized by assigning an AN value of 0 to the NMR shift obtained with hexane, and 100 to that obtained from the SbCl5:Et3PO interaction in dilute 1,2- dichloroethane solution. However, the total shift of 31P NMR in two-component systems has an appreciable contribution of van der Waals interactions that must be accounted for in correlating spectral shifts with heats of acid-base interactions. Riddle and Fowkes [7] corrected the 31P NMR shifts for van der Waals interactions and proposed a new scale of acceptor numbers. The new AN values (AN—ANd) in ppm are converted into AN* in kcal/mol units by
AN* = 0.228(AN — ANd) in kcal/mol (6)
where ANd is the dispersive component of the original AN values published by Gutmann.
Table 4 reports values of DN and AN* for a selection of solutes. It should be noted that since SbCl5 is a soft acid, the DN scale is thus a classification of softness for bases.
|
Liquid |
DN |
AN[2] |
|
Chloroform |
0 |
22.6 |
|
CH3NO2 |
11.3 |
18.0 |
|
Acetonitrile |
59 |
19.7 |
|
Water |
75.3 |
63.2 |
|
Acetone |
71.1 |
10.5 |
|
Ethyl acetate |
71.1 |
6.3 |
|
Diethylether |
80.3 |
5.9 |
|
THF |
83.7 |
2.1 |
|
Pyridine |
138.5 |
0.6 |
|
Dioxane |
61.9 |
0 |
Conversely, the AN* scale can be viewed as a scale of hardness for acids since Et3PO is a hard reference base. Nevertheless, the merit of Gutmann’s approach lies in the fact that his scales provide both acidic and basic parameters for amphoteric species, which is not the case with Drago’s E and C classifications.
Опубликовано в рубрике 