mass spectroscopy-(determination of structure) measurement of … · 2018-12-03 · mass...

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)


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


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




156/ C = C13Br (79) = C6 H7C13 to C12H12

C6H5Br C5H17Br?


112 = C9H4

Cl (35) = C2H11C9H4 => C8H16

C6H5Cl

M+ = 156

M+ = 112


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


H3C CH3

CH3H3C + CH3

H3C

CH3H3C

M-15


112

112

97

83

69

55 A B


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)




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


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)


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 H1

H

H5

H1

H6

H1H


H1 = H4

H1 H1

H

H5

H1

H6

H1H


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


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


HHH

H1

H2

H5

H4

H3


H4 = H3

HHH

H1

H2

H5

H4

H3


Bonus: How many Equivalent of H?

A. 6B. 5C. 4

mass spectroscopy-(determination of structure) measurement of … · 2018-12-03 · mass...

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