Читать книгу Biochemistry For Dummies - John Moore T., Richard Langley H., John T. Moore - Страница 60

The chemist Emil Fischer developed a method of drawing a compound to illustrate which stereoisomer was present. These Fischer projection formulas are very useful in biochemistry. In a projection formula, a chiral carbon is placed in the center of a + pattern. The vertical lines (bonds) point away from the viewer, and the horizontal lines point toward the viewer (see Figure 3-9). Fischer used the D designation if the most important group (the group whose central atom had the highest atomic number) was to the right of the carbon, and the L designation if the most important group (again, the group whose central atom has the highest atomic number) was to the left of the carbon. Figure 3-10 shows two Fischer projection formulas.

FIGURE 3-9: The construction of a Fischer projection.

FIGURE 3-10: Fischer projection formulas distinguish stereoisomers.

The d and l symbols for chiral substance forms aren’t necessarily the Fischer projection formula’s D- and L- forms, respectively; thus, confusion may occur and lead to incorrect predictions. For this reason, the use of d and l is diminishing. The use of D and L is gradually being replaced by the R and S system of designating isomers. This system is particularly useful when more than one chiral carbon atom is present. For a description of this system, see Organic Chemistry For Dummies, by Arthur Winter (Wiley)

Wow, that’s all the important organic chemistry you need for biochemistry in about 16 pages. How many pages did your organic chemistry text have, and what did it cost? This book is a real bargain!