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chemistry nucleophilic addition question

So in the attached file is the general equation for nucleophilic addition by my teacher. After the double bond turns into a single bond, the oxygen atom has a lone pair (as shown). Since It has this lone pair, hydrogen ion is attracted to it and it becomes an OH group. But since oxygen has 6 electrons in outer shell, this means that there is 1 other lone pair that we aren't drawing here, right? Then why doesn't another hydrogen ion attach to the oxygen molecule?

Thanks for any help I appreciate it

tsr help 8.1.JPG16.5KB

Reply 1

Kibser

The best way to think of how bonding works respective to different elements is the amount of bonds they tend to form. The general rule is that carbon will have 4 covalent bonds, nitrogen will have three covalent bonds, oxygen will have two covalent bonds and hydrogen will have just one. From that mechanism, you can see the intermediate species has an oxygen that's bonded only once, and therefore has a lone pair (electrons not used in the covalent bonding) which it will transfer to the hydrogen ion to form a second covalent bond.

Reply 2

Pigster

Original post by pondering-soul

Thanks for any help I appreciate it

If the H+ conc is high enough, it can cause another lone pair to be used forming a -OH₂⁺ group. This can fairly easily fall off, tending to produce an alkene (i.e. dehydration). This is assuming that either of the two C's you have shown have an H on them.