topic 7 + 19- modern analytical techniques 1+2

Question 1

what is made in fragmentation

Answer 1

ion and free radical
ion causes the peak

Question 1

peak with largest m/z in mass spec

Answer 1

parent ion/molecular ion

Question 2

waht affects peak intensity

Answer 2

the more STABLE the ion

Question 3

waht actually is IR

Answer 3

bonds absorb IR radiation at characteristic frequencies causing the bonds to vibrate

Question 4

IR below 1500

Answer 4

fingerprint region
unique for every compound

Question 5

H2,O2,N2

Answer 5

• CANT CHANGE POLARITY AS THEY VIBRATE
• asorb IR and dont register

Question 6

how does NMR work

Answer 6

• radio waves cause the the nucleus to change its spin state

Question 7

solvents for NMR

Answer 7

-DEUTERATED COMPOUNDS
- without 1H atoms, has 2H instead
- eg CCL4 (non polar)
- CDCL3 (polar)

Question 8

what is used to caliibrate NMR

Answer 8

TMS (tetramethylsilane)

Question 9

why is TMS used

Answer 9

• signal at 0
• 1 signal
• inert
• non toxic
• low BP can be removed easily

Question 10

ppm meaning

Answer 10

parts per millioin
relative to TMS

Question 11

IR Used for

Answer 11

functional group identification

Question 12

steps for a full identification

Answer 12

1. combustion analysis for empirical formula
2. mass spec to calculate molecular ion eak
3. IR for function groups
4. NMR

Question 13

why might there not be a molecular ion peak

Answer 13

its unstable