Cyclopropane molecular model

Wnte structural formulas or make molecular models for all the compounds that are tnchloro derivatives of cyclopropane (Don t forget to include stereoisomers ) Which are chiraL Which are achiral" ... 

In keeping with the "bent-bond" description of Figure 3.10, the carbon-carbon bond distance in cyclopropane (151 pm) is slightly shorter than that of ethane (153 pm) and cyclohexane (154 pm). The calculated values from molecular models (see Learning By Modeling) reproduce these experimental values. 

Because of their cyclic structures, cycloalkanes have two faces as viewed edge-on, a "top" face and a "bottom" face. As a result, isomerism is possible in substituted cycloalkanes. For example, there are two different 1,2-dimethyl-cyclopropane isomers, one with the two methyl groups on the same face of the ring and one with the methyls on opposite faces (Figure 4.2). Both isomers are stable compounds, and neither can be converted into the other without breaking and reforming chemical bonds. Make molecular models to prove this to yourself. 

Cyclopentenones. from 1.4-diketones. 886-887 Cyclopropane, angle strain in, 115 bent bonds in. 115 from alkenes. 227-229 molecular model of, 111. 115 strain energy of, 114 torsional strain in, 115 Cystathionine, cysteine from. 1177 Cysteine, biosynthesis of, 1177 disulfide bridges from, 1029 structure and properties of, 1018 Cytosine, electrostatic potential map of, 1104... 

The term cycloethane , as used here and in Reference 20d, generally makes more immediate sense to individuals used to molecular models with flexible bonds, whether they be metal springs or plastic tubes, than to those individuals who are used to model sets with lobes or fans to convey orbitals. The term cycloethane is also in interesting historical and linguistic counterpoint to the early chemical literature wherein trimethylene was often used in lieu of cyclopropane. For... 

FIGURE 1.16 Isomers of cyclopropane-1,2-dicarboxylic acid, (a) is-l,2-Dicarboxycyclopropane (trans isomers) (b) Z-l,2-Dicarboxycyclopropane isomer, (meso isomer) (c) Molecular models of E- (trans-) 1,2-dimethylcyclo-propane shown in the tube representation. Rotation of the right hand structure about a vertical axis through the center of the cyclopropane will superimpose the two methyl groups. The methylene of the rotated structure will be in the back, rather than the front, and not superimposed, (d) A mirror plane through the methylene and the back carbon-carbon bond is a plane of symmetry. The two carboxyl groups appear not to reflect each other in the model shown but they can rotate freely and will reflect each other on an instantaneous basis. 

Chiral dirhodium(II) tetrakis(methyl-2-oxopyrrolidine-5-carboxylates) and dirhodium(ll) tetrakis(4-benzyl-2-oxazolidinones) have been studied to determine factors influencing the enantiocontrol in metal-carbene transformations. Doyle et al. used the Tektronix CAChe molecular modeling system to examine the steric control on the optical yields of cyclopropanation products.Details of the force field are not available in the open literature. The low energy conformation of the proposed metal-carbene intermediate predicted absolute configurations of the product that conflicted with experiment. However, when the metal-carbene was weakly bonded to styrene, the low energy conformer... 

Cyclopropane was first prepared by reaction of 1,3-dibromopropane with sodium metal. Formulate the cyclopropane-forming reaction and then predict the product of the following reaction. What geometry do you expect for the product (Try building a molecular model.)... 

Molecular models are available for all the reactions and intermediates invoked in these mechanisms. For example, diazoalkanes have been known to generate metal-carbene complexes, with the cyclopropanation of metal-metal double bonds under smooth conditions (compare Section 3.1.7) being of particular relevance to the chemistry of metal surfaces, cf. eq. (10) [8 a, 23],... 

Make molecular models of CIS- and trans-1,2-dimethyl-cyclopropane, and compare their strain energies. 

Disregarding the possibility of transfusion of the cyclopropane ring with the five- and the slx-membered ring reduces the number of stereoisomers of the toxlsterols C to four as represented In Figure 21. Inspection of molecular models shows that Isomer I Is without unfavorable sterlc features. In Isomer II there Is crowding of the methyl groups CH3-I8 and CH3-I9, whereas In Isomers III and IV ring C must have a boat conformation. 

Make molecular models of cyclopropane through cyclododecane. Compare the relative conformational flexibility of each ring with that of others within the series and with that of the corresponding straight-chain alkanes. 

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