Saw horse projection

It IS no accident that sections of our chair cyclohexane drawings resemble saw horse projections of staggered conformations of alkanes The same spatial relationships seen m alkanes carry over to substituents on a six membered ring In the structure... 

Figure 2.2 Newman and saw horse projections for n-butane. (a) A staggered state (planar trans) with angle of bond rotation (j> = 0 and (b) an eclipsed state (planar cis) with = 180°.

Exercise 19-10 Draw saw-horse and projection formulas for each of the following compounds, and designate whether the particular enantiomer is erythro, threo, cis, or trans ... 

Fig. 2. Planar zigzag projection of the backbone carbon atoms of a) isotactic and b) syndiotactic polypropylene, both in the saw-horse and in the Fischer notation. It should be noted that the latter notation is not strictly a Fischer projection formula, because, by the Fischer convention, the carbon chain is always written vertically. In addition, only the methyl group positions are...

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