NMR and Chemical Tests Exam Question || OCR Chemistry || Level of Response

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@kiransumra5576 6 ай бұрын

Thank you for the video! I have a question: why do carboxylic acids, esters and amides not react with 2,4 DNHP and form an orange precipitate even if they do have the C=O bond?

@mrmurraygreen 6 ай бұрын

Your A-level limits ‘carbonyls’ to aldehydes and ketones and states that these are the only groups you need to know will form the ppt with 24DNP 👍🏻

@HarryKingwood 6 ай бұрын

Hi at 8.39. If you put peak at 2.4ppm quartet and 3 neighbouring but only put CH2 instead of ch3-ch2-co is that still considered correct or do you need the full structure at 2.4ppm to get the mark if that makes sense thanks

@mrmurraygreen 6 ай бұрын

Edited! Sorry my initial reply misread what you asked! You should always show the immediate other section of the molecule that the peak you are analysing is bonded to. Use the chemical shift scale to identify possible functional groups and the splitting pattern to identify other H’s. That way I am able to say it’s not just a CH2 but instead a CH3-CH2-CO! Does that make sense? Does that answer your Q?

@HarryKingwood 6 ай бұрын

@@mrmurraygreenwanted to double check if you could get the mark without it. Because on some mark schemes the ch2 for example is in bold and the neighbouring aren’t. Sometimes I struggle with the neighbouring assignment and just the ch2 which would be in bold in the mark scheme but would that get you the marks e.g if it was for 4 marks and 1 mark represented one chemical shift analysis

@HarryKingwood 6 ай бұрын

@@mrmurraygreenif I’m stuck on what the neighbouring is would it be best to put the ch2 only which in mark schemes are bold or try and guess the neighbouring assignment . Cause for these they are usually 6 marks and 4/6 according to my teacher is for analysis for the nmr and since I stuggle with the final structure I am happy with getting the 4 analysis marks thanks

@mrmurraygreen 6 ай бұрын

The bit in bold is the mark scheme’s way of showing what part of the molecule is responsible for the peak you are reporting on. You need to try and include the stuff around it to get the full analysis marks. Here are some general tips: How many H’s are in a peak comes from the relative peak area You can determine what functional groups it is bonded to based on its chemical shift data. Then you know how many H’s are on the next carbon(s) up based on the splitting pattern (and the n+1) rule. If you would like more practice with NMR then check out the year 2 playlist on my channel as there are lots of NMR tutorials in there.

@HarryKingwood 6 ай бұрын

@@mrmurraygreen thanks and one more questions if you get everything correct like all the analysis and attempted final answer but get it wrong how many marks can you get if it’s a six marker