Lectures_3-6 - 1 ORGANIC CHEMISTRY 307 Fall 2011 NOTES...

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Unformatted text preview: 1 ORGANIC CHEMISTRY 307 Fall 2011 NOTES Lectures 3-6 R. Boikess 1. . I. Overall Organization and Systematization As we have seen, focusing on functional groups, is one of the approaches we use to systemize the enormous amount of information about the chemical behavior of organic compounds. But even more basic than that we must have a way to describe, designate, and communicate about organic compounds . How well you master these skills will be a major determinant in how you do this year. a. Remember why there are so many compounds (C-C bonds and chains). So one focus is to describe the carbon skeleton, which consists of a “main” chain (the longest continuous chain) of C atoms with various additional C atoms or groups of C atoms (smaller chains) attached at various points. b. Think of it as a “connect the dots puzzle” with “branches” allowed. Let’s draw a big grid of dots and then connect. Do for 3 dots, 4 dots, 5 dots and 6 dots. Each different pattern of attachment corresponds to a different carbon skeleton, which is the starting point for describing and naming all organic compounds. Note it’s the pattern of attachment that counts, how many dots a given dot is connected to, not how we draw it , straight, zig-zag, or bent. Note that we have drawn three connected dots in three ways using the pink color. They look different, but they are the same because the pattern of attachment is the same. Similarly we use the green color to connect four dots in the same pattern of attachment, drawn three different ways. But we use the purple line to connect the four dots in a different pattern. These observations tell us that there is only one skeleton of 3 C atoms, but that there are two skeletons of 4 C atoms 2 Notice that we could connect dots in closed loops (called rings), which are different because the pattern of attachment is different. We have ignored that possibility in the analysis so far, but will come back to this point later. For 10 dots there are 75 ways, for 25 dots almost 36.8 million ways (not counting rings). That’s why this is a whole- year course. 3 b. How do we go from a carbon skeleton to a compound? Every C must have 4 bonds. Most carbons in most compounds get to 4 bonds by bearing the sufficient number of hydrogens. d. We simplify our descriptions by defining 1 , 2 , and 3 carbons , related to the number of C’s to which a given C is attached. Again, go from Kekule to condensed formulas and to condensed formulas with parentheses. [CH 3 (CH 2 ) 4 CH 3 and CH 3 C(C 2 H 5 ) 2 CH 3 ] e. Go from dots to skeletal structures, by focusing on the connections not the dots. We bend the lines so that a vertex of an angle represents a dot, which is a carbon atom. The end of a line is also a carbon atom....
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This note was uploaded on 11/17/2011 for the course ORGANIC CH 307 taught by Professor Boikes during the Fall '09 term at Rutgers.

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Lectures_3-6 - 1 ORGANIC CHEMISTRY 307 Fall 2011 NOTES...

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