A LEVEL CHEMISTRY EXAM QUESTION WALKTHROUGH - ORGANIC CONVERSIONS 24

Añadido: 2026-06-06

[00:00:00]Another question for the organic conversions topics. So, this is number 24. If you want to check out the other videos in the playlist, I'll put the link to that at the top of the screen now.

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[00:00:20]Okay, so we'll make a start. So, a typical question this one where we've got to fill in a flow chart. We've got this structure here and we've also got this structure at the end here. So, do the top half first. So, we've got to turn this given structure here into an acyl chloride. So, it's the carboxylic acid group that's going to react. And to turn a carboxylic acid into an acyl chloride, you use a chemical called thionyl chloride, which has the chemical formula SOCl2.

[00:00:53]So, the structure of the acyl chloride is that there.

[00:00:57]The next reaction where we react the acyl chloride with an excess of ammonia, well, the ammonia is going to react with the acyl chloride group. And basically, we're just going to change the Cl for an NH2 group and create an amide, which means the structure of that product looks like that.

[00:01:18]So, if you look at this reaction here now, so sodium hydroxide reacting with the original molecule, well, sodium hydroxide's going to react with the carboxylic acid group, going to get a neutralization reaction. And we're basically going to get the sodium salt of the acid, which has this structure here.

[00:01:39]Moving on to the bottom half of the flow chart now, so I'll do this reaction first. So, we're reacting the original molecule with a mixture of methanol and sulfuric acid. So, the alcohol is going to react with the carboxylic acid group and form an ester, which has that structure there.

[00:01:56]So, we'll finish off with this two-step process because we've got to factor in the final product to inform us what needs to go here and here.

[00:02:06]So, if we think about what's changed, so the fundamental difference is we've gone from four carbons to five carbons. So, we're going to need to introduce the nitrile group into this original molecule to increase the carbon count.

[00:02:21]But, the other thing we've got to factor in is that the C double bond O has changed into a C O H. So, we're going to need to turn this into a hydroxy nitrile before we can turn it into this final product. So, in terms of reagents, you could either say hydrogen cyanide or you could give a mixture, something like potassium cyanide or sodium cyanide and an acid. So, I've gone for sulfuric acid, you could go for nitric or hydrochloric. You could even just go for H+ there.

[00:02:54]So, there's the structure of the intermediate compound. I'll just quickly explain what's happening. So, the CN- ion is obviously joined onto this carbon here.

[00:03:02]So, I've got that there on my structure and the H+ has bonded with the O there, so we've got the OH group.

[00:03:12]And just to finish off, just I'm just going to quickly explain what's happened here. So, you can see I've highlighted this CH2CH3 group because it's in a slightly different position on the final product. So, that's just that there.

[00:03:27]And the CN group, the nitrile group, has become CH2NH2.

[00:03:33]So, you can see that's there, CH2 NH2. And obviously that's done by reacting the hydroxy nitrile with a mixture of hydrogen and nickel.