[sidharth]

I have 2,3-Dimethylbutane and mcmurry says that it has 3 staggred conformers. but I think that it has only two distinct  staggred conformers because the last two conformers have same relative position of groups. Am I correct?

Here is the picture of the 3 staggred conformers given in the study guide of the book

[Yggdrasil]

I think the last two conformers are mirror images of each other, so they are distinct.

[Smrt guy]

Remember that you're looking at a frozen rotation about a C-C single bond.  So you can tell if two rotamers are equivalent by rotating the entire molecule in space (you cannot rotate the bonds) and see if you can make them superimposable.  If you cannot, then they are distinct rotamers.

[roya_kindflower]

I think the last two conformers are mirror images of each other, so they are distinct.

But they have the plane of symmetry and same CH₃and H groups!Surely they are not chiral and are superimposable,right?

[Yggdrasil]

But they have the plane of symmetry and same CH₃and H groups!Surely they are not chiral and are superimposable,right?

Those two particular conformers do not have a plane of symmetry (although if you rotate bonds to the conformation shown on the far left it will have a plane of symmetry).  If you don't believe me, try building models and superposing them.

[sidharth]

I think the last two conformers are mirror images of each other, so they are distinct.

thanks man they are mirror images of each other  and so  are distinct.