1. CH3CHBrCH2Br
2. CH3CH2CHClCH2CH3
3. 2-bromo-2-methylpropane
4. 2,3-dimethylpentane
5. 5-fluoro-2,4-dimethylhex-1-ene

I wonder which of these contain optical isomers and why?

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What structural feature generates optical isomerization? Which of these compounds have it? (One of them will have 2 pairs of enantiomers!)