A chemist obtained spectral data of pentane-1,5-diamine (C5H12N2) - HSC - SSCE Chemistry - Question 29 - 2021 - Paper 1
Question 29
A chemist obtained spectral data of pentane-1,5-diamine (C5H12N2).
H2N
H2N
Infrared spectrum
Mass spectrum
(Mass of molecular ion: 102)
Proton NMR
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Worked Solution & Example Answer:A chemist obtained spectral data of pentane-1,5-diamine (C5H12N2) - HSC - SSCE Chemistry - Question 29 - 2021 - Paper 1
Step 1
Infrared spectrum
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Answer
The peak at the wave number range 3300–3400 cm⁻¹ is indicative of the N–H stretching vibration corresponding to the amino group in pentane-1,5-diamine. This aligns with the presence of the amine functional groups in the compound's structure.
Step 2
Mass spectrum
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Answer
The mass spectrum highlights the fragment
CH₂NH₂⁺, where the provided calculations show that the molecular ion corresponds to the derived structure of pentane-1,5-diamine (C₅H₁₂N₂). The calculated values confirm the expected structure is consistent with the mass data.
Step 3
Carbon-13 NMR spectrum
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In the carbon-13 NMR spectrum, there are only three unique signals despite having five carbon atoms in pentane-1,5-diamine. Due to symmetrical positioning, carbons 1 and 5 are equivalent, leading to fewer observed peaks, which supports the molecular structure.
Step 4
Proton NMR
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The Proton NMR shows a complex splitting pattern where the quintets arise from protons on adjacent carbon atoms. Notably, the presence of 4 H atoms in triplet and quintet configurations suggests specific neighboring environments, confirming the structure with collaboration from the other spectral data.
