The R and S enantiomers of an optically active compound differ in:

1. Their optical rotation of plane-polarized light.

2. Their reactivity with chiral reagents.

3. Their solubility in achiral reagents.

4. Their melting points.

The most stable conformation of n-butane among the following is:

1.		2.
3.		4.

The pair of structures given below represent-