Cycloalkanes , also polymethylene hydrocarbons [1] , naphthenes , cyclanes , or cycloparaffins - cyclic saturated hydrocarbons , are close to saturated hydrocarbons in chemical properties. They are part of the oil . Discovered by V. V. Markovnikov in 1883 from Baku oil [2]
In the petrochemical industry, naphthenes are a source of aromatic hydrocarbons by catalytic reforming . Cyclohexane , which is used for the synthesis of caprolactam , adipic acid and other compounds used in the production of synthetic fibers, has gained the greatest practical importance.
To cycloalkanes are saturated hydrocarbons with the general formula C n H 2n having a cyclic structure. The names of cycloalkanes are constructed from the names of the corresponding alkanes with the addition of the prefix cyclo- ( cyclopropane , 1,3-dimethylcyclohexane).
The following types of isomerism are characteristic of cycloalkanes:
- Isomerism of the carbon skeleton;
- Spatial;
- Interclass isomerism with alkenes .
All carbon atoms in cycloalkane molecules have sp³ hybridization. However, the angles between the hybrid orbitals in cyclobutane and especially in cyclopropane are not 109 ° 28 ', but smaller due to the geometry, which creates tension in the molecules, so small cycles are very reactive. Cyclopropane is used for anesthesia , but its use is limited due to the explosion hazard.
Content
- 1 Physical properties
- 2 Preparation of cycloalkanes
- 3 Chemical properties
- 4 notes
- 5 Literature
Physical Properties
Under normal conditions, the first two members of the series (C 3 - C 4 ) are gases, (C 5 - C 11 ) are liquids, starting with C 12 are solids. The boiling and melting points of cycloalkanes are higher than those of the corresponding alkanes . Cycloalkanes practically do not dissolve in water. With an increase in the number of carbon atoms , the molar mass increases, therefore, the melting temperature increases.
The melting and boiling points of some cycloalkanes:
| Cycloalkane | T. pl., ° C | T. boiling. ° C |
|---|---|---|
| cyclopropane C 3 H 6 | −126.9 | −32.7 |
| cyclobutane C 4 H 8 | −50 | 12 |
| cyclopentane C 5 H 10 | −93.9 | 49.3 |
| cyclohexane C 6 H 12 | 6.5 | 80 |
| cycloheptane C 7 H 14 | −12 | 118.5 |
| cyclooctane C 8 H 16 | 14.3 | 63 at 45 mmHg Art. |
| cyclononan C 9 H 18 | 9.7 | 69 at 14 mmHg Art. |
| cyclodecan C 10 H 20 | 10.8 | 201 |
| cycloundecane C 11 H 22 | −7.2 | 91 at 12 mmHg Art. |
| cyclododecane C 12 H 24 | 61.6 | 243 |
| cyclotridecane C 13 H 26 | 23.5 | 128 at 20 mmHg Art. |
| cyclotetradecane C 14 H 28 | 54 | 131 at 11 mmHg. Art. |
| cyclopentadecane C 15 H 30 | 62.1 | 147 at 12 mmHg. Art. |
Getting cycloalkanes
- Dehalogenation of dihalogen derivatives:
- Br — CH 2 —CH 2 —CH 2 —Br + Mg or Zn = cyclopropane + MgBr 2 or ZnBr 2
- Hydrogenation of benzene and its homologs (cyclohexane or its derivatives are formed):
- C 6 H 6 + 3H 2 = C 6 H 12
Chemical Properties
The chemical properties of small and ordinary cycles differ significantly from each other. Cyclopropane and cyclobutane are prone to addition reactions, that is, they are similar in this respect to alkenes . Cyclopentane and cyclohexane in their chemical behavior are close to alkanes , since they enter into substitution reactions.
- Cyclopropane and cyclobutane are able to attach bromine :
- C 3 H 6 + Br 2 → BrCH 2 —CH 2 —CH 2 Br
- Also, cyclopropane and cyclobutane can attach hydrogen halides, the addition occurs with the opening of the cycle, according to Markovnikov .
- Cyclopropane, cyclobutane and cyclopentane can add hydrogen , giving the corresponding normal alkanes. Joining occurs when heated in the presence of a nickel catalyst:
- C 4 H 8 + H 2 → CH 3 —CH 2 —CH 2 —CH 3
Notes
- ↑ Polymethylene hydrocarbons // Big Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
- ↑ Vladimir Vasilievich Markovnikov (1838-1904) [1948 - - People of Russian science. Volume 1 ] . nplit.ru. Date of treatment November 21, 2015.
Literature
- Kuzmenko N.E., Eremin V.V., Popkov V.A. The beginning of chemistry. The modern course for applicants to universities .. - M .: Exam, 2002.