[humble student]

Hey guys how's it going? I was working through a few problems where I had to figure out the mechanisms to convert a compound to another one. I spent a good amount of time trying to figure them out and I got a few but the 2nd, 3rd, and 5th ones in the image that I've attached have been giving me problems. If anyone had time to spare I would appreciate it if you would take a look at them and help me get onto the right track. Thanks in advance!

[humble student]

For the 2nd one I was thinking that some kind of nucleophilic addition followed by oxidation might work.
For the 3rd  and 5th ones however I'm not sure

[Dan]

For the 2nd one I was thinking that some kind of nucleophilic addition followed by oxidation might work.

Not a bad idea at all. Though depending on the nucleophile you may not need an oxidation. Concentrate on the carbons of the nucleohile - you need to add one carbon. What one-carbon nucleophiles do you know?

For the 3rd  and 5th ones however I'm not sure

For the 3rd - what reactions of benzene do you know? Which reactions of benzene result in C-C bond formation?
For the 5th - I suspect there may be an error here. Check the structures have been copied down correctly. Are you sure the product is not supposed to be this:

[humble student]

Thank you so much! I think I might know what to do. How does this sound:

For number 2 I think nucleophilic addition of -CN forming a cyanohydrin followed by hydrolysis of the Cyano group.

For number 3 Friedel Crafts acylation with a benze as the R of the acyl group

For number 5 I double checked and made sure I copied it correctly (I had). For that one I'll start by using an acetal as a protecting group to shield the ketone and then reduce the ester by a reducing agent like LiAlH4. Then use an aqueous acid to convert the acetal back into a ketone. Since the carbonyl group has a partial positive charge and there are free electrons on the OH group, those two will bond through nucleophilic addition. For stability the H on the resulting ether will shift to the oxygen double bonded to the  carbonyl carbon and I'll be left with the desired product.

[Dan]

For number 2 I think nucleophilic addition of -CN forming a cyanohydrin followed by hydrolysis of the Cyano group.

For number 3 Friedel Crafts acylation with a benze as the R of the acyl group

Sounds good

For number 5 I double checked and made sure I copied it correctly (I had). For that one I'll start by using an acetal as a protecting group to shield the ketone and then reduce the ester by a reducing agent like LiAlH4. Then use an aqueous acid to convert the acetal back into a ketone. Since the carbonyl group has a partial positive charge and there are free electrons on the OH group, those two will bond through nucleophilic addition. For stability the H on the resulting ether will shift to the oxygen double bonded to the  carbonyl carbon and I'll be left with the desired product.

That will give you the compound I drew, but not the one you drew.

[humble student]

I was thinking that that might be solved with a simple methyl shift.