Structural diagrams alkanes

As you learned earlier in this chapter, three kinds of diagrams can be used to represent the structure of a hydrocarbon. The easiest kind is probably the condensed structural diagram. When you are asked to draw a condensed structural diagram for an alkane, such as 2,3-dimethylhexane, you can follow several simple rules. These rules are listed below. After you have studied the rules, use the Practice Problems to practise your alkane-drawing skills. 

Draw a condensed structural diagram for each alkane. 

Figure 5.5 Structural diagram showing the molecular packing in odd n-alkanes (ric 11) with an orthorhombic c stalline structure as a projection on a diametrical plane, dc, that forms an angle of 45° with the ac and be planes of the costal.

Proton transfer from alkane radical cations that are in their electronic ground state is greatly facilitated by the fact that in mixed n-alkane crystals planar chain-end C-H bonds, from which proton donation takes place, come into close contact with secondary C-H bonds in adjacent molecules (see the structural diagrams below). In neat n-alkane crystals, there is only dose contact with primary C-H bonds that have much lower protonation energies. 

Given the name (or structural diagram) of a normal, branched, or halogen-substimted alkane, write the structural diagram (or name). 

Is the general formula of a cycloalkane the same as the general formula of an alkane, Cj,H2 . 2 Draw any structural diagrams to illustrate your answer. 

Haloalkanes can be regarded as substituted alkanes in which one or more of the hydrogen atoms is replaced by a halogen atom. They are named in a similar fashion to branched-chain alkanes with the halogen atoms treated like branches. For example, the anaesthetic halothane has the structure shown in the diagram and is called 2-bromo-2-chloro-l,l, 1-trifluoroethane. 

The alkanes you have studied so far are called straight-chain alkanes because the carbon atoms are bonded to each other in a single line. Now look at the two structures in the following diagram. If you count the carbon and hydrogen atoms, you will discover that both structures have the same molecular formula, C4Hio- E)o these structures represent the same substance ... 

If you said that all of these structures represent the same compound, you are correct. The diagram simply shows four ways of drawing a structural formula for 2-methylbutane. As you can see, the structural formula for a given hydrocarbon can be written in several ways. Before you continue reading, make sure that you understand why these structural formulas are all alike. You ll soon learn, however, that three distinctly different alkanes have the molecular formula C5H12. 

Figure 6 also displays the connection between the stable hexagonal phase in short n-alkanes and the hexagonal mesophase in polyethylene as a function of chain length in the p-T diagram. A full discussion is given by one of us elsewhere (6). At this place our emphasis is on the continuity, despite the fact that the pressure coefficient of the width of the temperature interval is of opposite sign in these two families of material. This continuity is apparent also by a structural feature, namely the concentration of conforma-... 

The pattern of bond lengths obtained by quantum chemical (QC) methods is almost identical for all of the alkanes and alkyl moieties given. The structures of alkanes are always easily predicted (see CH4 above) i.e. the vertical spread of points in the diagrams is always less than for the X-X... 

The role of Young diagrams in the ordering of chemical structures is explained by their relation to alkane hydrocarbons and unbranched cata-condensed benzenoid systems. 

Fig. 2.3.8. The variation of the nematic-isotropic transition 7J, with the number of methylene groups in the flexible spacer for a,co-bis(4,4 -cyanobiphenyloxy)alkanes, the molecular structure of which is shown at the top of the diagram. The dashed lines represent the theoretically calculated values. (After Luckhurst.< >)...

In previous chapters we discussed the ways reagents attack organic substrates (e.g., nucleophilic substitution, addition reactions and elimination reactions). Let us examine some interesting ways that C—C bonds can be broken in a homolytic manner which, in turn, lead to unusual predictions concerning reaction paths or intermediate structures. We start this discussion with a simple example of homolytic C—C bond cleavage in an alkane. A correlation diagram for this process is displayed in 11.51. 

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