Structural analysis Flashcards
IR stretch c=o
1780-1650
IR stretch c=n
2260-2220
benzene / phenyl
1600 and 1500-1430
1600 and 1500-1430
benzene / phenyl
2260-2220
IR stretch c=n
1780-1650
IR stretch c=o
o-h alcohol
3650-3200
o-h carboxylic acid
3300- 2500
3300- 2500
o-h carboxylic acid
3650-3200
o-h alcohol
if a mass spec has two lines for m+ it means …
it has a atom with an isotope (maybe br or cl is present)
mass spec : 29 means ….
ch2-ch3 chain (ethyl group)
mass spec : 127 means ….
iodine
mass spec: to signify iodine we may see…
127 and a large gap to the next group
if br or cl is present , the m+ line is likely to look like what?
two lines for m+ because they can have an isotope
mass spec : 77 means ….
phenyl group
m*+1 = x . how do we work out how many carbons?
x/1.1
HNMR: how can we work out if its a ch, ch2 or ch3 easily?
use the integration. if we know what one integral represents, we can compare this value to work out how many Hs are present in the others.
mass spec : 91 means ….
tropylium aka benzene with a ch2
HNMR: when two protons are coupled, the coupling constant is …
the same for both protons.
(therefore we can tell which peaks on hnmr are potentially coupled).
HNMR: if the signals are zoomed in but look different, this is because…
they may be taken at different frequencies. look carefully to see if they have been taken under different equipment.
HMRS (High resolution mass spectrometry)
sum of the exact values of the masses of the most common isotope eg c-12.00000 h+1.007825
HNMR: isopropyl group looks like …
septuplet
very small coupling constants mean that its a…
long range coupling
ennantiomers are ….
if you swith the protons for x, they are mirror images or each other.
diastereomers are…
if you swith protons for x, they are totally different molecules. can occur when switching for x creates two or more chiral centres (doesnt always occur)
ir- alcohol
broad round band at 3200-3400
ir- alkene ch
sharp stalegtite shape band at above 3000
ir - alkane ch
sharp stalegtite shape band at below 3000
ir carbonyls c=o
strong very sharp pointy stretch at 1700
ir alkene c=c
a few sharp bands at around 1600
ir single c-o bond
medium thickness v shaped band at 1100
ir alkyne ch
sharp medium intensity at 3300
ir NH
either a very intense sharp band (maybe more for nh) or a slighly broader, less intense w shape . both at 3500.
hnmr sections as we increase from 0
(not ppm just numbered for ease)
1- alkane and alkane like hydrogens
2- hydrogens adjacent to an unstaurated bond eg ketones or allylic hydrogens
3- SP hydrogens on a triple bond
4- hydrogens adjacent to electronegative atoms
5- Alkene SP2 hydrogens
6- Aromatic hydrogens
7- Aldehydes
Calculating J values for first order splitting eg s d t q q s etc
will only have one J value.
(ppm1(highest but also doesnt matter really as long as they are next to eachother)-ppm2) x frequency of NMR machine
Calculating J values for second order splitting eg dd dt dq etc
will have 2 J values.
J1= (ppmbigpart1-ppmsamebigpartin2) x freq NMR machine
J2= ppm1-ppm2 (like you do for first order splitting)
J1 = J value of overall doublet
J2= J value of mini doublets
coupling constanats are highest for dihedral angles of …. and lowest for dihedral angles of….
highest 180. lowest 0
