mass spectroscopy-(determination of structure) measurement of … · 2018-12-03 · mass...
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Mass Spectroscopy-(Determination of Structure)Measurement of Mass (M) to Charge Ratio (Z) (M/Z)
r = mv/qB r = radiusm = massv = velocityq = chargeB = Magnetic Field
Klein, Organic Chemistry, 3e
Mass Spectroscopy-Measurement of Mass to Charge Ratio M/Z (Determination of Structure)
• Parent Ion (M+)• Intact Mass of the Compound• Could be used to calculate the chemical formula of the
unknown
• Fragmented Ion • Structural information• Could be used to determine the structure of the
compound
H3C
H2C C
H2
H2C CH3 H3C
H2C C
H2
CH2 + CH3
Degree of unsaturation:
• Degree of unsaturation = • (2 X #C + 2 + #N - #H - #X)/2
• Tell you no of π bond or cyclic structure,
• E.g. 1 = 1 double bond or 1 cyclic structure• 2 = 2 double bond or 1 triple bond or 2 cyclic
structure or 1 cyclic structure + 1 double bond
Analyzing M+(Parent ion)
Klein, Organic Chemistry, 3e
Analyzing M+(Parent ion)
• Here we got M+ = 72
• We take 72 divided by Molecular Weight (MW) of Carbon which is 12
• It is equal to 6, means the molecular formula could be C6, less likely, so we can convert 1 C to 12 H,
• Which will become C5H12, or it could be C4H24 (very less likely), could also be C4H8O
• Degree of unsaturaton: (#C *2 + 2 + #N - #X - #H)/2
• The molecular formula for alkane - CnH(2n+2), alkene – CnH2n or alkyne – CnH(2n-2)
• Nitrogen rule, • Parent ion is odd number, odd number of nitrogen• Parent ion is even number, even number of nitrogen Klein, Organic Chemistry, 3e
What is the molecular formula (Only has C and H)?
112/ C = C9H4convert 1 C to 12HC8H16, 1 degree of unsaturation
112
112
97
83
69
55
Klein, Organic Chemistry, 3e
Analyzing M+2 (Chlorinated or Brominated compounds)
One Bromine, M: M+2 = 1:1
One Chlorine, M: M+2 = 3:1
M+ = 156
M+ = 112
Klein, Organic Chemistry, 3e
Analyzing M+2 (Chlorinated or Brominated compounds)
One Bromine, M: M+2 = 1:1
156/ C = C13Br (79) = C6 H7C13 to C12H12
C6H5Br C5H17Br?
One Chlorine, M: M+2 = 3:1
112 = C9H4
Cl (35) = C2H11C9H4 => C8H16
C6H5Cl
M+ = 156
M+ = 112
Klein, Organic Chemistry, 3e
Analyzing M+2 (Chlorinated or Brominated compounds)
One Bromine, M: M+2 = 1:1
One Chlorine, M: M+2 = 3:1
Klein, Organic Chemistry, 3e
https://webbook.nist.gov/cgi/cbook.cgi?Spec=C121448&Index=0&Type=Mass&Large=on
Nitrogen Rule
M+ = 101
https://webbook.nist.gov/cgi/cbook.cgi?Spec=C121448&Index=0&Type=Mass&Large=on
Odd M+ , Odd number of Nitrogen
101/ C = C8H5
N (14) = C1H2
C7H3N or
C6H15N
M+ = 101
Mass Spectroscopy-Measurement of Mass to Charge Ratio M/Z (Determination of Structure)
• Parent Ion (M+)• Intact Mass of the Compound• Could be used to calculate the chemical formula of the
unknown
• Fragmented Ion • Structural information• Could be used to determine the structure of the
compound
H3C
H2C C
H2
H2C CH3 H3C
H2C C
H2
CH2 + CH3
57
4129
7257
43
29
H3C
H2C C
H2
H2C CH3
H3C CH3
CH3H3C
A B
Bonus
Klein, Organic Chemistry, 3e
H3C CH3
CH3H3C + CH3
H3C
CH3H3C
M-15
Klein, Organic Chemistry, 3e
112
112
97
83
69
55 A B
Klein, Organic Chemistry, 3e
112
112
97
83
69
55 A B
Klein, Organic Chemistry, 3e
Proton and Carbon NMR
Information provided by H-NMR
• Identify functional group• Identify the part of the structure• Identify the connection of different part of the
structure• Determine the complete chemical structure.
1. Different kind of Proton – functional group(Chemical Shift)
Information provided by H-NMR
Klein, Organic Chemistry, 3e
Information provided by H-NMR
1. Different kind of Proton (Chemical Shift)
2. Proton Ratio of Different Proton (Peaks area)Klein, Organic Chemistry, 3e
3. Number of Neighbouring Proton (N+1 rule)
Information provided by H-NMRKlein, Organic Chemistry, 3e
Information provided by H-NMR
1. Different kind of Proton – Functional Group
(Chemical Shift)
2. Proton Ratio of Different Proton (Peaks area)3. Number of Neighbouring Proton (N+1 rule)
Klein, Organic Chemistry, 3e
Functional Group based on Chemical Shift
https://www2.chemistry.msu.edu/courses/cem251/SS13_HOVIG/Spectroscopy%20tables.pdf
Chemically Equivalence (For non-Chiral Compounds)
H4 H1
H
H5
H3
H6
H2H
H1 = H2 = H3
H4 H2
H
H5
H1
H6
H3H
Chemically Equivalence
H1 = H2 = H3
H4 H2
H
H5
H1
H6
H3H
Chemically Equivalence
H1 = H2 = H3
H4 H1
H
H5
H1
H6
H1H
Chemically Equivalence
H1 = H4
H1 H1
H
H5
H1
H6
H1H
Chemically Equivalence
H5 = H6
Enantiomeric H
H1 H1
H
D5
H1
H5
H1H
H1 H1
H
H5
H1
D6
H1H
H1 H1
H
H5
H1
H5
H1H
Chemically Equivalence
6 x H12 x H5
https://study.com/academy/lesson/how-to-read-nmr-spectra-of-organic-compounds.html
Peak Area1:3
How many chemically equivalence H in this compound?
H1
H2
H5
H4
H3
How many chemically equivalence H in this compound?
HHH
H1
H2
H5
H4
H3
How many chemically equivalence H in this compound?
H4 = H3
HHH
H1
H2
H5
H4
H3
How many chemically equivalence H in this compound?
Bonus: How many Equivalent of H?
A. 6B. 5C. 4
Bonus: How many Equivalent of H?
A. 6B. 5C. 4
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