[Dolphinsiu]

Compound A is transformed to the antidepressant Bupropion [2-(tert-butylamino)-1-(3-chlorophenyl)propanone] via a series of reaction. The mass spectrum of A reveal strong signals at 168 and 170 with abundance 3:1. The elemental analysis with C = 64.11% and H = 5.38%. The proton nmr spectrum of A shows peak at 1.2(triplet, 3H);2.9(quartet, 2H) and 7.2 - 8.0 (multiplet, 4H). There is a strong peak at 1683 cm-1. Show your rationale and suggest a structure of A.

I have known A has disubstituted benzene and one Cl as (abundance 3:1)
but as strong peak at 1683 cm-1, it is secondary amide.
C:H = 1:1, as nmr give 9H's, then there is approximately about 9H's and 9C's.
Assume 9H's and 9C's is present
Molecular formula become C9H9NOCl (Molecular mass = 182)
But Cl and CONHCH3 attached to C6H4 (Molecular mass = 170)

It seems this structure does not match NMR (2H and 3H)

Do I get anything else wrong?

[Dolphinsiu]

Does anyone help?

[Alexander]

could you provide the NMR an IR spectras?
elemental analysis and NMR both show that there are 9 carbon and 9 hydrogen atoms. as much as I understand there are -CH₂-CH₃ and -C₆H₄- groups
usually using elemental analysis you can determin percentage of nitrogen. secondary amide group signal is in 3300-3600cm^-1. so I'm not sure about nitrogen.

[abk]

I'm pretty sure the compound is 1-(3-Chloro-phenyl)-propan-1-one, (m-Cl-Ph-CO-Ch2-Ch3). Exact mass 168.03. A triplet and quartet for -Ch2-Ch3. Meta substition b'cause Bupropion have same substitution.

[abk]

I think this is the structure of this compound.

[Custos]

Compound A is transformed to the antidepressant Bupropion [2-(tert-butylamino)-1-(3-chlorophenyl)propanone] via a series of reaction. The mass spectrum of A reveal strong signals at 168 and 170 with abundance 3:1. The elemental analysis with C = 64.11% and H = 5.38%. The proton nmr spectrum of A shows peak at 1.2(triplet, 3H);2.9(quartet, 2H) and 7.2 - 8.0 (multiplet, 4H). There is a strong peak at 1683 cm-1. Show your rationale and suggest a structure of A.

I have known A has disubstituted benzene and one Cl as (abundance 3:1)
but as strong peak at 1683 cm-1, it is secondary amide.
C:H = 1:1, as nmr give 9H's, then there is approximately about 9H's and 9C's.
Assume 9H's and 9C's is present
Molecular formula become C9H9NOCl (Molecular mass = 182)
But Cl and CONHCH3 attached to C6H4 (Molecular mass = 170)

It seems this structure does not match NMR (2H and 3H)

Do I get anything else wrong?

Your molecular weight is 168/170 (3:1), which as you say indicates a chlorine. It's also an even number which means an even number or no nitrogen atoms. Your compound probably has no nitrogen. Don't let the IR lead you astray - NMR and Mass Spec are much more diagnostic. The 1683 absorption is a carbonyl, but not necessarily an amide carbonyl. The NMR tells you you have an aromatic ring with 4 protons on it - hence disubstituted. The rest follows as posted by abk.

[Dolphinsiu]

Thank you!