2-methyl-trans-aconitate <=> 2-methyl-cis-aconitate
2-methyl-trans-aconitate <=> 2-methyl-cis-aconitate
2-methyl-trans-aconitate <=> 2-methyl-cis-aconitate
2-methyl-trans-aconitate <=> 2-methyl-cis-aconitate