reaction between cyclohexene and the sulphuric acid...what is the product?

Question

from the experiment...i found that there are three layers form:
upper layer: black color
middle layer: yellow color
lower layer: colorless

what are the things that form these color layers?

Answer 1

You shouldn't have three different liquid layers, so to speak, as you usually have only two layers, one organic and one aqueous.

One product you should obtain is cyclohexanol, since sulfuric acid can act as an acid catalyst in the addition of water (SN1 chemistry). However, sulfuric acid can also char any carbohydrate, and make a burnt black product. You can check this by putting some concentrated sulfuric acid onto some sugar...it will turn the sugar black (If you accidentally got it on your skin, it would char your skin too, but you might not notice it because you're in too much pain from it eating through your epidermis.). That's what the black product probably is, charring your cyclohexanol.

The colorless layer is probably your aqueous layer, and I use this term somewhat loosely. If you do not use water in your experiment, and the cyclohexene and cyclohexanol do not mix, then the colorless layer is cyclohexanol. Easy way to figure it out is to look at your starting material cyclohexene. Was it yellow?

Answer 2

Before dilution, the product would have been cyclohexyl hydrogensulphate. Of course this forms cyclohexanol on dilution, but, as with most organic syntheses, there are byproducts, and concentrated sulphuric acid is notorious in its ability to char organic material, ie turn it into black carbon.