Bonds in acyclic structures with vertical branches

Structure diagrams with vertical, single- or double-bonded, branches, going up or down, are frequently seen. Several experiments with TEX and LATEX were made to see how this type of structure can be handled. One method is to align the vertical bonds by using the mechanisms for tabbing or for printing tables and matrices. Here a structure such as the one shown in Figure [*] is treated as a set of columns as indicated by the vertical dividing lines drawn into the second version of this structure in Figure [*].

Figure: Vertical branches 

                    Br		 		 CH3 

 |		 		  |  


CH3CH2		 CH		 CHCH2		 
CHCH2CH3  

    | 


CH2CH3


   
CH3CH2|CH
|CHCH2
|CHCH2CH3                    |Br		 | 
|CH3                                                    

| |		 | |                                                     |  


CH3CH2		 |CH 
|CHCH2		 
|CHCH2CH3                                                     

|		 | | |                                                    

|		 
|CH2CH3

The structure diagram in Figure [*] uses \vert for the vertical bonds and LATEX's tabbing environment for the alignment. One can also use ``rules'' as the vertical bonds in order to give the horizontal and vertical bonds the same lengths. Furthermore, vertical bonds can also be double bonds. The following examples illustrate these features.

$\displaystyle \tbranch$ODH2N-C-NH21   $\displaystyle \tbranch$CH3-CH2-C-CH3DNH1   $\displaystyle \tbranch$H-C= SBr1$\displaystyle \tbranch$C-HSBr1

Similar structures were also generated with TEX's \halign mechanism which forms templates for the columns rather than setting tab stops. For the purpose of printing the structure diagrams, no clearcut advantage was seen in one or the other method of alignment. In each case the vertical spacing depends on the line spacing in the document.

The alternative method of producing these structures is the use of the picture environment. It provides better control over horizontal and vertical spacing and over bond lengths. Also, as illustrated in Section [*], using a picture environment makes it possible to attach one structural fragment to another at a specific place. Thus, although the picture environment is not necessary for drawing structures with vertical branches, it has several advantages, and writing LATEX code for this implementation is not more difficult than writing the code for the tabbing method of alignment.