A heavy topic but a one which will gain you marks! Watch this video to find out how spectra can be interpreted when you have molecules. Find out how to identify fragments and the need for high resolution mass spectrometry and GC-MS.
Thanks! So pleased I have made it a bit easier for you! Chemistry is a tough subject but it really doesn't have to be difficult and I am so pleased I have managed to get this across in a form that is easy to understand.
+Ross Scrivens Thanks! Pleased my explanation has made it clear for you. Difficult to tell if the explanation is clear enough until I get feedback like yours. Cheers!
I'm in Advanced Ochem at my uni and my professor's method of teaching is saying "you should know this by now." But I never fucking learned how to interpret Mass Spec. This video helped me out so much, thank you so much!
You are so amazing!!!Wow like I don't even remember how my teacher ever introduced this topic recently it's not that I have forgotten but I just never understood what was happening. And she thought she was explaining it the best way she can .....YOU are literally my life saver, I thank God I found you out just before my exams. Thank You , keep up the good work. It is helping a lot!!!
Thank you, found this video extremely helpful. You have a great way of speaking so that what you are explaining is very clear. Will definitely use you videos again :)
+Emily Farrell Thanks very much. It is useful to get feedback like yours, I have an idea how I would like it to be portrayed, however I never know how useful it is until I get feedback from people who use them. Thanks again.
Thanks for your comment! It's nice to see an international audience using them. Mind chemistry is an international science so maybe I should expect it. My fingers are crossed for your assessment. Although you may have sat the exam by now going off the mega difference in time zones! Ha!
Sorry if this sounds dumb but I saw how when mass fragmentation took place the molecular ion fragmented into a radical and a cation (from the previous vid) so how would we get CH2+ because that's right in the middle. So even if an electron is knocked off how would we get CH2+ and what would be the resulting radical? Thanks again for all these great vids! :)
+Mel tansz Yes during fragmentation the molecule can break anywhere on the carbon chain. Sometimes it can break multiple times not just in 2. Fragments form where the bonds are weakest. Hope this helps. Thanks for your positive comment too!☺
Hello Chris Harris hope you are doing well, i wanted to inquire if you do unit 3 Papers practical skills as you have brilliant helpful unit 2 tutorials.keep the fab work going !
+Ayoub syed Thanks very much! I will look into practical skills but only after the exams unfortunately. All the practical exams have had major changes for the new specs so will start them in September. Sorry I can't be of any use on that matter.
great explanation. very hard to find good resources in this. My orgo teachers dont even teach anything. we all have to be self taught. We dont even get practice problems that match the very difficult exams. I have not found one resource online that matcg his crazy synthesis problems
I am really confused. i was given a question to identify the peak 57 of butan 1 ol. Now it can be C4H9 as well as CH2OHCH2C assuming fragments can form from any where. how to identify
+fatima khan Fragmentation of C-H bonds are unlikely due to the high enthalpy value. You will more likely get C-C bonds and C-O bonds breaking which means your fragment at 57 will be C4H9.
Natalie Lyme Yes the M+1 peak is a molecule with molecular mass M however it will have an isotope of carbon 13 in the molecule making it heavier by one. We can say this as most mass spec is done with organic molecules that contain a lot of carbon. Hope this helps!
I'm not sure if you are still active on this video but I was just wondering..... what if you didn't know the molecular formula but just that it was a carboxylic acid? Would you just have to deduce everything instead?
Still live and kicking! Yes you would look for fragments like COOH+. It's important to note that you would never use one spectral technique to identify a compound. You would use a mix of techniques e.g. NMR and IR.
Allery Chemistry Thanks for the reply 😁 We're apparently expected to know this is in AS but only from IR and m/z spectra. It's all good now, thanks again 😁
I think that may not be possible. You have to attain so many marks to make up for the A. I think B is more likely if you score very highly in second year exams.
i started as chemistry this september i got two B's in science do you think i will find it difficult, also in GCSE i used bitesize but i can find any similar sites like that to revise for chemistry i aim to get my chemistry revision guide this week, also ive seen a book on amazon do you think i shoukd get it:www.amazon.co.uk/Calculations-AS-A-Level-Chemistry/dp/0582411270
+AJ' The most important thing is that you enjoy Chemistry. You are more likely to stick with it if you like it. Chemistry is a tough subject but if you work at it you will do well in it. I have never seen this book before but I would recommend an alternative guide that is user friendly which is published by CGP and is cheaper!. They do a maths skills book that will be released on the 16th of this month www.amazon.co.uk/New-2015-A-Level-Chemistry-Essential/dp/1782944729. They also do revision guides and a course book. Just make sure you get the correct board and for the NEW Spec. Obviously you can use these vids to help you too. I am about to update some of them to reflect the minor content changes. Mass spec has changed for example to 'time of flight' (TOF). My new podcasts cover this just follow this link www.allerytutors.libsyn.com/ Hope it goes well for you!
In theory, the fingerprint region could do this. However, you need a computer and library of known molecules to do this! So, in the absence of this, you can really only identify functional groups using IR. E.g. a molecule with the same mass but different functional group could be an alkene and a cycloalkane or an ether and an alcohol. IR could distinguish between these.
Hi Allery , would be great help if you would post the solution of ist question from the past year paper 9701_s_13_qp_42.. unable to understand how to show working on graphs and find out the half life from the constructed graph.PLEASE SEND . THANKS
iiCheesecake Yes there could be. These would be peaks that would be half the m/z value if it was just a +1 peak. E.g. CH2+ would have an m/z (mass/charge) of 14 (14/1=14) CH2+2 would be 7 (14/2=7). The key thing to remember here is m/z is a mass to charge ratio not just mass, hence the charge has a big effect on peak position.
Kouli. Yes if you used high resolution mass spectrometry. For simplicity I used whole numbers and this is what is used in the exam too. Hope this clears things up!
low sheng That is possible however very unlikely as 2 bonds would need to be broken to form that. A C-H bond requires a lot of energy to break. In this example a peak at 13 was not evident which suggests a CH fragment is not made. Hope this helps!
