isomers of glucose that differ in configurations at carbons one and four (C-1 and C-4)

a mixture of (D)-glucose and (L)-glucose

enantiomers of glucose

isomers of glucose that differ in configuration at carbon one (C-1)

cytosine and adenine

cytosine and guanine

cytosine and thymine

cytosine and uracil

$$3$$-bromo - $$1$$-chlorocyclohexene

$$1$$-bromo - $$3$$-chlorocyclohexene

$$2$$-bromo - $$6$$-chlorocyclohex - $$1$$ -ene

$$6$$-bromo - $$2$$ - chlorocyclohexene