4-Chloropentanal

Propylene, with acetyl chloride, aluminum chloride, and quinoline to give fnms-3- wnten-2-one, 51,115 with acetyl chloride and aluminum chloride to give 4-chloropentan-2-one, 51,116... 

Alenylacetylenes, 50,101 Aluminum chloride, with ethylene and p-methoxyphenylacetyl chloride to give 6-methoxy-/3-tetralone, 51,109 with propylene and acetyl chloride to give 4-chloropentan-2-one, 51,116 Amine oxides, anhydrous, 50, 55, 58 Amines, protecting group for, 50,12 AMINES FROM MIXED CARBOXYLIC-CARBONIC ANHYDRIDES 1-PHENYLCYCLOPENTYLAMINE,... 

STRATEGY AND ANSWER C2 and C4 are chirality centers in 2-bromO 4-chloropentane. We begin by drawing the carbon chain with as many carbons depicted in the plane of the paper as possible, and in a way that maximizes the symmetry between C2 and C4. In this case, an ordinary zig-zag bond-line formula provides symmetry between C2 and C4. Then we add the bromine and chlorine atoms at 02 and 04, respectively, as well as the hydrogen atoms at these carbons, resulting in formula I. To draw its enantiomer (II), we imagine a mirror and draw a reflection of the molecule. 

In substrates bearing more than one stereocenter, inversion takes place only at the carbons that undergo reaction with the incoming nucleophile. Note that the reaction of (25,4P)-2-bromo-4-chloropentane with excess cyanide ion results in a meso product. This outcome is particularly readily recognized using Fischer projections. 

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