Q11) I thought a compound can only have 1 molecular ion peak? Q12) I know the formula for atom economy but none of them give the correct value? :s
11) As there are two Br isotopes to consider and two Br in each molecule, you could have:
a) one with 79Br and 79Br b) one with 79Br and 81Br c) one with 81Br and 81Br
So you would have three peaks for the molecular ion.
There are often other peaks present around the molecular ion for an organic molecule (eg for when some carbon 13 is present), but the abundance of other isotopes is so small that these peaks are only tiny. For bromine the two isotopes have a bigger abundance relative to each other, hence you notice the peaks due to differing isotopes.
12) Remember it's (sum of Mr of useful products/sum of Mr of all products)x100 and make sure you've got the correct product as your useful product (a very easy mistake to make on these). It does work.
11) As there are two Br isotopes to consider and two Br in each molecule, you could have:
a) one with 79Br and 79Br b) one with 79Br and 81Br c) one with 81Br and 81Br
So you would have three peaks for the molecular ion.
There are often other peaks present around the molecular ion for an organic molecule (eg for when some carbon 13 is present), but the abundance of other isotopes is so small that these peaks are only tiny. For bromine the two isotopes have a bigger abundance relative to each other, hence you notice the peaks due to differing isotopes.
12) Remember it's (sum of Mr of useful products/sum of Mr of all products)x100 and make sure you've got the correct product as your useful product (a very easy mistake to make on these). It does work.
Oh I see.. How comes we don't consider the 1H and 12C isotopes?
Regarding Q12: I understand where I went wrong now! Whenever there is one product only, the atom economy is always 100% right?
Oh I see.. How comes we don't consider the 1H and 12C isotopes?
Regarding Q12: I understand where I went wrong now! Whenever there is one product only, the atom economy is always 100% right?
Thanks!
Ari has answered the first part for you. In general remember the abundance of the other isotopes of carbon and hydrogen is very small in comparision to C-12 and H-1.
re: the atom economy, absolutely if only one product the AE is 100%.
Ari has answered the first part for you. In general remember the abundance of the other isotopes of carbon and hydrogen is very small in comparision to C-12 and H-1.
re: the atom economy, absolutely if only one product the AE is 100%.