[Lindsay<3]

Hey guys, thank you so much for the help last time!

For this, im pretty sure I got the 2nd one right.


For the first, it looks like the hydride would deprotonate the OH, forming a negatively charged oxygen, and an sn2 reaction would take place with the Br to make a cyclic ether. But this confirmation is not anti, which is essential for the reaction to take place. what do i do?

For the third, it looks like the hydride would deprotonate the hydroxy group and a propane like ether would form at one end of the cyclohexane, with the sulfur group leaving. Wouldnt this propane ether be facing behind the plane? Now when heated in propanol, the ring would be open, but im confused as to what the stereochemistry would be

[macman104]

For the first one, you need to rotate the molecule until you get the two groups anti.  Then perform the sn2-like reaction, and draw with the stereochemistry you observe.  You are supposed to use the newman as a guide to predicting the stereochemistry of the reaction.

For the third one, there are two ways to open an epoxide:  activated or unactivated

In the activated mechanism, the epoxide is activated usually by an aqueous acid, or some lewis acid.  This causes the nucleophile to attack from the most stable carbocation location.

In the unactivated mechanism, the epoxide has no pretreatment.  The nucleophile simply has to force the epoxide open.  In these cases, the nucleophile usually attacks from the least hindered direction.

Which way do you think simply heating in propanol is, can you use that to predict where the propanol will open the epoxide?

[Lindsay<3]

thank you, you definetly set me on the right path!

1.) I think I got this product right, including inversion at the attacked carbon

2.) I think this is right, only problem i realized i might have is that CN is a very weak nucleophile... is it still able to carry out the SN2 reaction?

3. ) yes, the nucleophile definetly attacks from the least hindered direction. I think think the product here is right, does my final product have the right configuration? I checked weather R and S were switched and it looked right!

thank you in advance for any more *delete me*

[azmanam]

watch the direction of your arrows.  arrows flow from areas of high electron density to low electron density.  at least one arrow in the above mechanisms is backward and/or missing all together.

[macman104]

^What he said also.

1 and 2 look good to me.  Also, in the right solvents CN is a very good nucleophile.  For 3, it looks like you have the right configuration, but you did not draw propanol.