Cycloalkanes ring opening

C-C Bond Activation and Cycloalkane Ring-Opening by Transition Metal Atoms... 

Preparation of 2-Cycloalkenones and Cycloalkane-1,3-diones BY Iron(III) Chloride-Induced Ring Opening of 1-Trimethyi,-siLYLOxY- AND 1,2-Bis(trimethylsilyloxy)bicyclo[w.1.0]alkanes... 

Fig. 28 Nucleophilic ring opening of cyclic dimethylammonium ions [38], Free energies of activation relative to ring-size 6 against cycloalkane strain-energies. Energy units kcal mol"1. (Reproduced with permission from Di Vona et al., 1985)...

Reduction of cycloalkane-condensed 2-phenyl-5,6-dihydro-4//-l,3-benzoxazines 144 with lithium aluminium hydride (LAH) afforded A -benzyl-substituted 2-(aminomethyl)cycloalkanols 145 in a reductive ring opening via the ring-chain tautomeric tetrahydro-l,3-oxazine intermediates. Catalytic reduction of 1,3-oxazines 144 under mild conditions in the presence of palladium-on-carbon catalyst similarly resulted in formation of the A -benzyl-1,3-amino alcohols 145. When the catalytic reduction was performed at elevated temperature at hydrogen pressure of 7.1 MPa, the N-unsubstituted 2-(aminomethyl)cycloalkanols 146 were formed in good yields (Scheme 22) <1998SC2303>. 

Adsorption modes and hydrogenolysis were also correlated with other metal-catalyzed reactions. Gault noticed striking similarities in product distributions of isomerization and ring opening of cycloalkanes. Kinetic and tracer studies provided useful data252 268 to arrive at the conclusion that a common surface intermediate is... 

Hydrogenative ring opening of cycloalkanes is also a well-studied area.16 252 253 289-292 Mainly cyclopropanes and cyclopentanes were studied, since three- and five-membered adsorbed carbocyclic species are believed to be intermediates in metal-catalyzed isomerization of alkanes (see Section 4.3.1). Ring-opening reactivity of different ring systems decreases in the order cyclopropane > cyclobutane > cyclopentane > cyclohexane.251 Cyclopropane and its substituted derivatives usually react below 100°C. 

Exercise 12-17 Use the heats of combustion to liquid water given in Table 12-3 and appropriate bond energies to calculate AH° (vapor) for ring-opening of the cycloalkanes with bromine in the range n = 2 to n = 6 ... 

The isomerization of cycloalkanes over SbF5-intercalated graphite can be achieved at room temperature without the usual ring opening and cracking reactions, which occur at higher temperatures and lower acidities.110 In the presence of excess hydrocarbon after several hours, the thermodynamic equilibrium is reached for the isomers. Interconversion between cyclohexane (20) and methylcyclopentane (21) yields the thermodynamic equilibrium mixture [Eq. (5.46)]. 

These are used more often than cycloalkanes nevertheless they are far from being conventional monomers . They polymerize either as 1, 2-disub-stituted alkene derivatives [14] (without ring opening) or else the cyclic monomer is split, yielding a macrocycle or a linear chain (metathesis). 

When certain cycloalkanes are used in metathesis reactions, ring-opening metathesis polymerization (ROMP) occurs to form a high molecular weight polymer, as shown with cyclopentene as the starting material. The reaction is driven to completion by relief of strain in the cycloalkene. 

Holroyd studied the type of the radicals formed in irradiated cyclopropane with the radical sampling technique and found several intermediates besides the cyclopropyl radical. Not all the hydrocarbons formed were identified but it was found that cyclopropyl and allyl radicals were both present in approximately a 1 1 ratio, indicating that ring-opening is a major process in cyclopropane. The extent of ring-opening decreases for cyclobutane and decreases further for cyclopentane. Similar results that the probability of C-C bond rupture falls from cyclopropane to cyclohexane were observed in the radiolysis of liquid cycloalkanes in an ESR study. ... 

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