17.1 Mass spectrometry 0.0 / 5 ? ChemistrySpectroscopyA2/A-levelOCR Created by: ilee02Created on: 28-04-19 21:06 What happens when an organic compound is placed in the mass spectrometer? It loses an electron and forms a posiitve ion, the molecular ion 1 of 17 What is the definition of molecular ion? The positive ion formed in mass spectrometry when a molecule loses an electron 2 of 17 What does the mass spectrometer detect? The mass to charge ratio (m/z) of the molecular ion which gives the molecular mass of the compound 3 of 17 What needs to be located to find the molecular mass? The molecular ion peak (M+ peak) 4 of 17 What is the molecular ion peak? The clear peak at the highest m/z value on the right hand side of the mass spectrum 5 of 17 What is the very small peak one unit after the M+ peak referred to as? The M+1 peak 6 of 17 Why does the M+1 peak exist? Because 1.1% carbon is present as the carbon-13 isotope 7 of 17 What do some molecular ions break down into during mass spectrometry? Smaller pieces known as fragments 8 of 17 What is the definition of fragmentation? The porcess in mass spectrometry that causes a positive ion to split into smaller pieces, one of which is positive fragment ion 9 of 17 What are the other peaks in a mass spectrum caused by? Fragment ions, formed from the breakdown of the molecular ion 10 of 17 What does the simplest fragmentation break a molecular ion into? Two species - a positively charged fragment and an uncharged radical 11 of 17 Which species does a mass spectrometer detect? The positively charged fragment 12 of 17 Whic species doesn't a mass spectromter detect? The uncharged radical 13 of 17 Why is the mass spectrum of each compound unique? As all molecules fragment in slightly different ways depending on their strcutures. 14 of 17 What can mass spectra be used for? To help identify molecules 15 of 17 What can be different even if two molecules have the same molecular mass and the same molecular ion peak? The fragment ions found 16 of 17 What equations links number of carbon atoms, M+peak and M+1 peak? Number of carbon atoms = height of M+1 peak / height of M peak x100 17 of 17
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