CH3-CHCl-CH2Cl的一溴代物有3种:CH2Br-CHCl-CH2Cl、CH3-CBrCl-CH2Cl、CH3-CHCl-CHBrCl;
当一溴代物为CH2Br-CHCl-CH2Cl时,二溴代物有3种:CHBr2-CHCl-CH2Cl、CH2Br-CBrCl-CH2Cl、CH2Br-CHCl-CHBrCl、
当一溴代物为CH3-CBrCl-CH2Cl时,二溴代物有1种:CH3-CBrCl-CHBrCl;
当一溴代物为CH3-CHCl-CHBrCl时,二溴代物有1种:CH3-CHCl-CBr2Cl;
所以异丁烷的二氯代物的同分异构体共有5种;
故选C.