Question

Unknown Number:

Molecular Formula:

Index of Hydrogen Deficiency:

Structure:

Mass Spec

Molecular Weight:

Important Fragments; what are they and what do they mean? (base peak structure, is there a halogen, is there a benzene ring, is there an odd number of nitrogens, other important fragments that tell something about the structure)

IR

Is there an OH? Wavenumber?

Is there a carbonyl group? If so what type (acid. ester, amide, aldehyde, ketone etc.)?   Wave number?

Other important peaks (terminal alkyne, cyano group, aromatic, alkene, nitro group, amine etc.) and where are they?

¹H-NMR

Identify every signal; chemical shift, what is it due to( i.e what type of proton, aromatic, aldehydic, O-H, N-H, vinyl etc.) and how many protons does it represent.

¹³C-NMR

How many different types of carbons are present?

What type of carbon does each signal represent?

How can you put the skeleton together?

LOGIC:

Carefully, and thoroughly show how you used the spectral data to determine your structure. Show how all your data confirms your structure. Especially useful is using ¹H-NMR as confirmation.

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Answer 1

Molecular Formula: C₅H₁₂O₂.

Index of Hydrogen Deficiency: 0

Structure: CH₃-O-C(CH₃)₂-O-CH₃

Mass Spec

Molecular Weight: 104

what are they and what do they mean?

as per what is written on EI-MS molar mass is 104.

M- 15 mass units ==> m/z = 89 ( loss of -CH3 group )

base peak : 73 ( M- 31)

No odd number of nitrogens and No halogen present. No peak at 77 or 51 thus benzene ring absent.

IR

Is there an OH? No

Is there a carbonyl group? No

Other important peaks : 3000-2830 cm-1 due to sp3C-H stretching ; strong peak at 1084 cm-1 is due to C-O stretching (ether).

¹H-NMR : 2 singlets

• 1.3 ppm ( 6H , s)
• 3.2 ppm ( 6H , s) : down field ;;---> attached to heteroatom ,most probably 'O'.
• this indicates presence of 4 methyl (-CH3) groups).

¹³C-NMR

How many different types of carbons are present?

3

What type of carbon does each signal represent?

sp3 C /alkyl carbon : ,q indicates for -CH3 groups and singlet indicates for quaternary C.

downfield peaks 49 and 98 ppm due to attached 'O' atom.

How can you put the skeleton together?

total No. of cabon seems to be five ( 2+2+1 )

==

4 methyl (-CH3) groups) and 1 quaternary C accounts for : 72 mass units.

104 - 72 = 32 ==> can be accounted for presence of 2 'O' atoms.

Molecular Formula: C₅H₁₂O₂.

Structure: CH₃-O-C(CH₃)₂-O-CH₃