2-butanol Fischer projection

It IS customary to orient the molecule so that the carbon chain is vertical with the lowest numbered carbon at the top as shown for the Fischer projection of (R) 2 butanol... 

Using the Fischer projection of (/ ) 2 butanol that was given at... 

Draw Fischer projections or make molecular models of the four stereoisomeric 3 ammo 2 butanols and label each erythro or threo as appropriate... 

Make a molecular model corresponding to the stereochem istry of the Fischer projection of 2 phenyl 2 butanol shown in the equation and verify that it has the R configuration... 

SAMPLE SOLUTION (a) Exchanging the positions of H and OH in the Fischer projection of (R)-2-butanol converts it to the mirror-image Fischer projection. The configuration of the chirality center goes from R to S. 

The sawhorse or Newman representations of 2-butanol, 5a and 5b and 6a and 6b, are excellent for showing the arrangements of the atoms in conformations, but are needlessly complex for representing the stereochemical configuration. Fischer projection formulas are widely used to show configurations and are quite straightforward, once one gets the idea of what they represent. 

Which of the following projection formulas represent the same isomer Write each in its proper form as a Fischer projection formula of 3-amino-2-butanol. 

If the lowest priority group is in a vertical position, determine whether the sequence of the remaining three groups (1 2 3) is clockwise (R) or counterclockwise (S). In this case, it is clockwise and the Fischer projection represents (S)-2-butanol. 

Knowing the two rules provides a way to see if two projections reproi sent the same or different enantiomers, For example, three different Fischer projections of 2-butanol follow. Do all represent the same enantiomer, or is one different ... 

Practice Problem 9.4 Convert the following tetrahedral representation of (l )-2-butanol into a Fischer projection ... 

Applying the above strategy to CR)-2-butanol gives the following Fischer projection ... 

Many organic compounds have more than one asymmetric carbon. The more asymmetric carbons a compound has, the more stereoisomers are possible for the compound. If we know how many asymmetric carbons a compound has, we can calculate the maximum number of stereoisomers for that compound a compound can have a maximum of 2 stereoisomers (provided it doesn t have any other stereocenters), where n equals the number of asymmetric carbons. For example, 3-chloro-2-butanol has two asymmetric carbons. Therefore, it can have as many as four (2 = 4) stereoisomers. The four stereoisomers are shown both as perspective formulas and as Fischer projections. 

When Fischer projections are drawn for stereoisomers with two adjacent asymmetric carbons (such as those for 3-chloro-2-butanol), the enantiomers with similar... 

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