Email: support@essaywriterpros.com
Call Us: US - +1 845 478 5244 | UK - +44 20 7193 7850 | AUS - +61 2 8005 4826

Comparison with analogues


In aqueous solutions hydrogen peroxide differs from the pure substance due to the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water form a eutectic mixture, exhibiting freezing-point depression; pure water has a freezing point of 0 °C and pure hydrogen peroxide of −0.43 °C. The boiling point of the same mixtures is also depressed in relation with the mean of both boiling points (125.1 °C). It occurs at 114 °C. This boiling point is 14 °C greater than that of pure water and 36.2 °C less than that of pure hydrogen peroxide.[7]

Phase diagram of H
2O
2 and water: Area above blue line is liquid. Dotted lines separate solid+liquid phases from solid+solid phases.

H2O2 (w/w)Density
(g/cm3)
Temp.
(°C)
3%1.009515
27%1.1020
35%1.1320
50%1.2020
70%1.2920
75%1.3320
96%1.4220
98%1.4320
100%1.4520

Structure

Hydrogen peroxide (H
2O
2) is a nonplanar molecule as shown by Paul-Antoine Giguère in 1950 using infrared spectroscopy,[8][9] with (twisted) C2 symmetry. Although the O−O bond is a single bond, the molecule has a relatively high rotational barrier of 2460 cm−1(29.45 kJ/mol);[10] for comparison, the rotational barrier for ethane is 12.5 kJ/mol. The increased barrier is ascribed to repulsion between the lone pairs of the adjacent oxygen atoms and results in hydrogen peroxide displaying atropisomerism.

The molecular structures of gaseous and crystalline H
2O
2 are significantly different. This difference is attributed to the effects of hydrogen bonding, which is absent in the gaseous state.[11] Crystals of H
2O
2 are tetragonal with the space group D4
4P4121.[12]

O−O bond length=147.4 pm O−H bond length=95.0 pm

Structure and dimensions of H2O2 in the gas phase

O−O bond length=145.8 pm O−H bond length=98.8 pm

Structure and dimensions of H2O2 in the solid (crystalline) phase

NameFormulaMolar mass
(g/mol)
Melting
point (°C)
Boiling
point (°C)
Hydrogen peroxideHOOH34.01−0.43150.2*
WaterHOH18.020.0099.98
Hydrogen disulfideHSSH66.15−89.670.7
HydrazineH2NNH232.052114
HydroxylamineNH2OH33.033358*
DiphosphaneH2PPH265.98−9963.5*