ringalkane(hu á n w á n t ī ng), containing alicyclic structureSaturated hydrocarbon。There are monocyclic alicyclic andFused ringAlicyclic.It contains one aliphatic ring and there is no substitution on the ringalkylNaphthenic hydrocarbon with the general formula CnH2n（n≧3）。Cyclopentane、cyclohexaneAnd their alkyl substituted derivatives arepetroleum productsCycloalkanes commonly found in.Polycyclic cycloalkanes exist at high boiling pointsPetroleum fractionMedium.Cycloalkanes have a highCalorific value，freezing pointLow, antiknock property is between normal hydrocarbon and isomeric hydrocarbon.chemical propertySimilar to alkanes.Among them, the properties of five carbon alicyclic ring and six carbon alicyclic ring are more stable.
twochemical property: (1) The chemical properties of cycloalkanes with large rings such as five membered rings and six membered rings are very similar to those of chain alkanes, which are similar to those of acids, bases, oxidants andreducing agentGenerally, they do not react when exposed to light, heated at high temperature or heated atperoxideIt can also happen if it existsFree radicalSubstitution reaction。[1]
1. Classification of naphthenic hydrocarbon: (1) By carbon number:carbon atomWhen the number is 3~4, it is called small ring;When it is 5~6, it is calledOrdinary ring；When it is 7-12, it is called the middle ring;When it is greater than 12, it is calledMacrocycle。(2) According to the number of rings: if there is only one ring in the molecule, it is called a single ring;Two rings are called double rings;It is called multi ring if there are three or more rings.(3) According to the combination mode of rings: two rings share one carbon atom——Screw ring；Two rings share two carbon atoms——Fused ring；Two rings share more than two carbon atoms - bridge ring.
2. Name: (1) Single ring: add a "ring" before the name of the corresponding open chain hydrocarbon, if anyfunctional groupMake its position number the smallest or make the substituent have the lowest serial number as far as possible.(2) Polycyclic: In addition to adding the word "ring" before the name of the open chain hydrocarbon, it is also necessary to indicate the number of rings and the number of carbon atoms between the two bridgehead carbon atoms, which are separated by "·" and enclosed in square brackets.
Alicyclic hydrocarbon can also contain more than two carbon rings, which can be connected in many ways: two rings in the molecule can share onecarbon atomThis system is calledScrew ring；The two carbon atoms on the ring can be connected by carbon bridge to form a double ring or multi ring system, called bridge ring;Several rings can also be connected with each other to form a cage structure.
The designation of monocyclic hydrocarbons is to use ring characters to represent cyclohydrocarbons, use propane, butyl, and pentane to represent the number of carbon atoms in the ring, and use alkanes, alkenes, and alkynes to represent onlySingle bondOr double bondTriple bond, substituent expression method andAlkaneSame.Bicyclic hydrocarbon is called bicyclic alkane (or alkene) according to the total number of carbon atoms in the ringsquare bracketsInternal useArabic numeralsIndicates the number of carbon atoms on each carbon bridge connecting the carbon atoms at the bridgehead. Write firstMacrocycleCarbon ofAtomic number。If the two bridgehead carbon atoms are directly connected, the number of carbon atoms on the bridge is 0.Arabic numerals are separated by dots.The name of a spiro ring is similar to that of a bicyclic compound. It is called spiro alkane (or alkene) according to the total number of carbon atoms on the ring. Arabic numerals are used in square brackets to indicate the number of carbon atoms on two rings except for the shared carbon atoms. Write the number of carbon atoms on the small ring first.More complex compounds are commonly used by conventional names.
takeBoat conformationThe carbon of is twisted about 30 ° to become a boat twisting type:
cyclohexaneCompared with the boat type, the torsion boat type conformation of the flagpole bond has lower hydrogen non bond tension;7kJ lower than boat conformation·mol-1
In the chair conformation of cyclohexane, sixcarbon atomOn two parallel planes respectively.C1, C3 and C5 are on the upper plane, and C2, C4 and C6 are on the lower plane.Cyclohexane ring has a tripleAxis of symmetryPerpendicular to one of the planes.
