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Properties of substance:

p-benzoquinone



skc-file

Group of substances:

organic

Physical appearance:

yellow monoclinic crystals

Empirical formula (Hill's system for organic substances):

C6H4O2

Molar/atomic mass: 108.095

Melting point (°C):

115.7

Solubility (g/100 g of solvent):

deuterium oxide: 1.37 (20°C) [Ref.]
diethyl ether: soluble [Ref.]
ethanol: soluble [Ref.]
hydrogen fluoride : very soluble [Ref.]
ligroin: soluble (100°C) [Ref.]
petroleum ether: sparingly soluble [Ref.]
water: 0.7 (5°C) [Ref.]
water: 1.5 (30°C) [Ref.]

Density:

1.318 (20°C, g/cm3)

Synthesis 1:

Reference: Храмкина М.Н. Практикум по органическому синтезу. - Л.: Химия, 1977 pp. 200-201



10 gr of hydroquinone and 100 ml of water warmed up to 50 C is placed in a round-bottom flask. After dissolving of hydroquinone the mixture is cooled until 20 C and 5 ml of sulfuric acid, acting as a catalyst, is added slowly in small portions.

In case of using not very pure hydroquinone black sticky precipitate immediately forms after the addition of sulfuric acid. To get rid of this precipitate the mixture is filtered through a folded filter before adding an oxidizing agent, in this case it's potassium bromate.

5,5 gr of potassium bromate is added to the reaction mixture with caution, the flask is heated on a water bath to 60 C. The reaction starts immediately with a formation of green-black precipitate - hyngidrone. The heating is stopped as the temperature rises to 75 C. The oxidizing reaction is considered completed as soon as the black colour of the reaction mixture changes to bright-yellow colour of benzoquinone. The reaction mixture is heated to 80 C until the full dissolving of benzoquinone, then it is cooled until 0 C. Precipitated para-benzoquinone is filtered using a Buchner funnel, rinsed with a small amount of ice water and dried.

The yield o p-benzoquinone (melting point is 116 C) is approximately 8 gr.

Permittivity (dielectric constant):

3.12 (17°C)

Standard molar enthalpy (heat) of formation ΔfH0 (298.15 K, kJ/mol):

-185.7 (s)

Molar heat capacity at constant pressure Cp (298.15 K, J/(mol·K)):

129 (s)

Molar enthalpy (heat) of fusion ΔfusH (kJ/mol):

20.95

Enthalpy (heat) of vaporization ΔvapH (kJ/mol):

47.76

Standard molar enthalpy (heat) of formation ΔfH0 (298.15 K, kJ/mol):

-122.9 (g)

References:

  1. CRC Handbook of Chemistry and Physics. - 90ed. - CRC Press, 2010. - pp. 5-31
  2. Seidell A. Solubilities of organic compounds. - 3ed., vol.2. - New York: D. Van Nostrand Company, 1941. - pp. 343-345
  3. Yalkowsky S.H., Yan H. Handbook of aqueous solubility data. - CRC Press, 2003. - pp. 219
  4. Общая органическая химия. - Т. 2, под ред. Бартона Д. и Оллиса В.Д. - М.: Химия, 1982. - pp. 840-846 [Russian]
  5. Рабинович В.А., Хавин З.Я. Краткий химический справочник. - Л.: Химия, 1977. - pp. 131 [Russian]
  6. Успехи химии. - 1991. - Т.60, №1. - pp. 134-168 [Russian]
  7. Химическая энциклопедия. - Т. 1. - М.: Советская энциклопедия, 1988. - pp. 278-279 [Russian]

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    © Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru