organic chemistry analysis and spectroscopy

Question 1

how is proton NMR used in medicine ?

Answer 1

magnetic resonance imaging/providing diagnostic information/body scanners.

Question 2

reigon of EM spectrum H NMR uses?

Answer 2

radio waves

Question 3

how to know the nuber of carbon environments?

Answer 3

count the proejctions on the graph

Question 4

why is cdcl3 used in hnmr (2)

Answer 4

The solvent does not have any hydrogen/H/protons to prevent (1H nuclei from) the solvent from interfering with the NMR spectrum

Question 5

regarding H nmr, where in the data sheet should you look ?

Answer 5

the HYDROGENS in BOLD writing, the intergration number refers to how many bold hydrogens are attached here

the ppm is simply the group that this hydrogen is attached to

Question 6

why is TMS used? (1)

Answer 6

TMS/tetramethylsilane (which is the) standard (for chemical shift measurements)

Question 7

give a model answer for this NMR question (9 marks)

5 marks for NMR analysis

4 marks for drawign the correct structure

Answer 7

NMR ANALYSIS

how to naswer this: start off by stating the differetn groups shown at different NMR’s

M1: Peak(s) at (δ) 9.7 = CHO

M2: Peak(s) at (δ) 7.1 = C6H4

M3: Triplet at (δ) 1.3/peak at 1.3 AND quartet (at δ 2.6)/ peak at 2.6 = CH2CH3

M4: Triplet at (δ) 9.7/peak at 9.7 AND doublet (at δ 3.7)/peak at 3.7 = CH2CHO

(DONT forget to get mark 5 by showing the “n+1” rule!)

M5: (n+1 rule) Any one of the following • triplet at (δ) 1.3 shows (C with) 2 adjacent Hs/protons OR adjacent CH2 (because of splitting: so triplet)

( i got the structure correct )

Question 8

what could a H nmr spectra peak with an intergration number of 6 mean ?

Answer 8

either one whole benzene , or the more likely situiation ..

HCH(CH3)2

Question 9

what information can be derived from intergration traces ( 1)

Answer 9

the number of hydrogens in each environment

NOT

“The number of hydrogens in the compound”

Question 10

how could a chemist use results from gas chromatography to predict the number of esters in a mixture and their relative proprotions ?

Answer 10

(number of esters) from number of peaks/retention times AND (proportions) from (relative) peak areas

Question 11

how do we identify the type of compound from gas chromatogrpahy ?

and why would there be unertainty about using gas chromatography alone to predict the number of different types of esters ?

Answer 11

by retention time

some esters have similar retention times therefore they could come out of the gas chromatograph at the same tine , making it hard to identify the different types of esters

Question 12

important thing to do in NMR questiosn ?

Answer 12

list the variable they ask for and then give yoru reasoning

eg: proton nmr, mass spectra, c13 nmr

Question 13

NOTE : ALWAYS MOVE THE PEAK IF THE QUESTION SAYS ITS SHIFTED

Question 14

what does D2O do ?

Answer 14

replaces the “H” in OH or NH protoons with D

eg ch3oh–. CH3OD

Question 15

Compound F was found to be present in the smoke. Compound F contains C, H and O only and contains 54.2% oxygen by mass. The molar mass of compound F is 118.0 g mol–1. (i) Using the information, show that the molecular formula of compound F is C4H6O4. Show all of your working

Answer 15

note; after findign the moles of oxygen…

TAKE AWAY ITS MASS FROM OVERALL MASS

AND THEN PROVE THAT C4H10 IS PRESENT BY MULTIPLYIGN EACH BY MR AND THEN ADDING UP!!!

Question 16

Compounds in the smoke from forest fires can be analysed using GC-MS. Explain how GC-MS enables the compounds to be identified.

Answer 16

idea of separating (the components/compounds)  idea of (identifying compounds) by comparison with a (spectral) database

Question 17

Why would compounds be deteurated before H nmr spectra

Answer 17

because non-deteurated compounds would causse a peak to show, thus interrupting the spectra

Question 18

steps to identifying chemicals from C nmr ?

Answer 18

1. identify the number of environments
2. link to each functional group ]

note, as you can see here,

stated that…

“there are 4 different carbon environments”

NOTE: position of the lines and position of the carbon environemnts DO NOT HAVE ANY CORELATION