Thermodynamic Quantities for the Ionization Reactions of Buffers

272 GOLDBERG, KISHORE, AND LENNEN
TABLE 7.25. Diglycolate
Other names 2,2-oxydiacetic acid; diglycolic acid; 2,2-oxybisacetic acid; diglycollic acid; 3-oxapentanedioic acid; 2,2-oxydiethanoic acid;
CAS No. 110-99-6
Empirical formula C 4H 6O 5
Molecular weight 134.09
Ionization reactions
H 2LH HL (1)
HL H L 2 (2)
where H 2LC 4H 6O 5
Selected values at TÄ298.15 K and IÄ0:
pK3.05, rG°/(kJ mol 1 )17.41, rH°/(kJ mol 1 )0.1, and rC p /(J K 1 mol 1 )142 for reaction 1
pK4.37, rG°/(kJ mol 1 )24.94, rH°/(kJ mol 1 )7.2, and rC p /(J K 1 mol 1 )138 for reaction 2
Evaluation: reaction 1, BCD; reaction 2, BCD
Structure:
Values from literature
pK rH°/(kJ mol 1 ) T/K I Methods and comments Reference
Reaction „1…: H 2LÄH ¿ ¿HL À
2.90 303.15 0.1 M Glass electrode; spectrophotometry. 57TIC/BEN
2.77 298.15 0.1 M Glass electrode. 60YAS/YAM
3.06 293.15 0.1 M Potentiometric titration—glass electrode. 61CAM/OST
2.80 293.15 1.0 M Potentiometric titration—quinhydrone electrode. 63GRE/TOB
2.69 1.6 298.15 1.0 M Potentiometric titration; calorimetry. 69GRE/HAN
2.91 298.15 2.0 M Glass electrode; Spectrophotometry. 72APL/NOI
2.83
2.83
278.15
293.15
1.0 M
1.0 M
Potentiometric titration—quinhydrone electrode. The value of rH° is calculated from the temperature dependence of the pKs.
72GRE/OTS
0.66 298.15 1.0 M
2.81 303.15 1.0 M
2.81 323.15 1.0 M
2.85 338.15 1.0 M
4.13
1.76
278.15
293.15
1.0 M
1.0 M
1 1 Calorimetry. The value rC p/(J K mol )142 is calculated
from the temperature dependence of the rH° values.
72GRE/OTS2
0.11 308.15 1.0 M
2.40 323.15 1.0 M
2.80 298.15 0.5 M Potentiometric titration—glass electrode. 72NAP
2.82 293.15 1.0 M Potentiometric titration—glass electrode. 73CAS/DIB
2.73 298.15 0.1 M Potentiometric titration—glass electrode. 74MIY/SHI
2.78 298.15 0.1 M Potentiometric titration—glass electrode. 75FIE/COB
2.83 298.15 0.1 M Potentiometric titration—glass electrode. 78ARE/MUS
2.81 298.15 0.1 M Potentiometric titration—glass electrode. 79HOG/NIL
2.67 298.15 0.1 M Potentiometric titration—glass electrode. 79SIN/DUB
2.88 308.15 0.1 M
2.96 318.15 0.1 M
3.05 0.84 298.15 0 Potentiometric titration—glass electrode; calorimetry. 80CAL/RIZ
2.80 298.15 0.5 M Potentiometric titration—glass electrode. 81NAP/PAO
2.73 298.15 0 Potentiometric titration—glass electrode. 83DUB/BEW
2.82 298.15 0.1 M Potentiometric titration—glass electrode. 84MOT/MAR2
3.06 298.15 0 Potentiometric titration—glass electrode. 85CAP/DER
2.97 4 298.15 0 Potentiometric titration—glass electrode. 85DAN/DER
3.07 283.15 0 Potentiometric titration—glass electrode. The value of rH° given
3.05 293.15 0
3.05 1.2 298.15 0
3.04 303.15 0
3.05 313.15 0
3.06 323.15 0
J. Phys. Chem. Ref. Data, Vol. 31, No. 2, 2002
here was calculated from pKs measured at several temperatures. The
value rC p /(J K 1 mol 1 )182 was also calculated from the
temperature dependency of their 90DER/DES reported pKs.
90DER/DES