# Hello, can you please tell me the interpretation of this IR spectra of "1-(2,4-dinitrophenyl)-2""-(propan-2-ylidene)""hydrazine"?? Thanks in advance

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May 18, 2017

Based on this spectrum of nitrobenzene from SDBS (http://sdbs.db.aist.go.jp/), I don't think the ${\text{1618 cm}}^{- 1}$ is the imine bond. I think that is one of the ${\text{NO}}_{2}$ stretches, since they are very similar shapes.

It may be the weak $\boldsymbol{{\text{1689 cm}}^{- 1}}$ peak. I don't know how strong or weak it's supposed to be, but it does reasonably match the first reference spectrum I showed.

(I am referring to the weak shoulder to the left of the two nitro stretches.)

If not, it may be the $\boldsymbol{{\text{1587 cm}}^{- 1}}$ peak, since the two nitro groups on the same benzene ring may withdraw electron density away from the imine bond, weakening it.

(A weaker bond has a lower force constant and thus a lower fundamental stretching frequency.)

I searched your compound on http://scifinder.cas.org/, and landed on:

REFERENCE FREQUENCIES

From my text (Techniques in Organic Chemistry 3rd ed. by Mohrig), these are the relevant reference frequencies that I can find off-hand:

• $\boldsymbol{{\text{NO}}_{2}}$ stretches (${\text{1570 - 1490 cm"^(-1), "1390 - 1300 cm}}^{- 1}$, strong)
• Aromatic
$\text{C"="C}$ stretch (${\text{1620 - 1440 cm}}^{- 1}$, medium to weak),
$\text{C"-"H}$ stretch (${\text{3100 - 3000 cm}}^{- 1}$, medium to weak),
$\text{C"-"H}$ bend ($\text{900 - 680 cm"^(-1)}$, strong)
• Amines
$\text{N"-"H}$ stretch (${\text{3550 - 3250 cm}}^{- 1}$, medium;
${2}^{\circ}$ amine $\implies$ one band)
• Alkanes
$\text{C"-"H}$ stretch (${\text{2990 - 2850 cm}}^{- 1}$, medium to strong)

Overall, here's what I came up with:

REFERENCE SPECTRA

Since the amine frequencies weren't clear, another reference spectrum is from the Integrated Spectral Database System of Organic Compounds (National Institute of Advanced Industrial Science and Technology [Japan]), taken with a JASCO FT/IR-410:

Lastly, this website reports about ${\text{1660 cm}}^{- 1}$ for the $\text{C"="N}$ stretch.

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