The homotopic methyls at (a) and the unique H at (b) form an isopropyl (1-methylethyl) group, with an extremely characteristic pattern: doublet + septet, 6 : 1 integration ratio. As is often the case, we must expand the septet region to be able to see all seven peaks; if such an expansion is not available, the absorption may be referred to as a "multiplet", meaning "There's a bunch of lines there, but I can't quite count 'em!"
The pattern of the hydrogens on the benzene ring, (c) and (d), is also typical - typical for a 1,4-disubstituted benzene (para-disubstituted) with groups that differ distinctly, so that the hydrogens next to one substituent are in a significantly different environment than those next to the other. The two widely separated doublets (one neighbor) show clearly in the expansion.
The benzene chemical shift arises from an induced circulation of electrons:
The aldehyde H in R-CHO is usually found shifted downfield to the neighborhood of 9.5 ppm by an induced circulation of thep-electrons of the C=O. In Ar-CHO the additional circulation of the p-electrons of the benzene ring produces a further shift, to the vicinity of 10 ppm.
| Cuminaldehyde | |
| Synonym(s) | Cumaldehyde Cuminal Cuminic aldehyde p-Isopropylbenzaldehyde |
| Latest JECFA evaluation | 2001 (Session 57) |
| Status of specification | Full |
| Chemical name | 4-Isopropylbenzaldehye |
| JECFA number | 868 |
| CAS number | 122-03-2 |
| FEMA number | 2341 |
| COE number | 111 |
| FLAVIS number | - |
| Molecular weight | 148.2 |
| Chemical formula | C10H12O |
| Physical form/odour | colourless to pale yellow liquid with a strong, pungent, spicy, green, herbaceous odour |
| Solubility | insoluble in water; soluble in organic solvents, oils |
| Solubility in ethanol | miscible at room temperature |
| Boiling point (°C) | 235-236° |
| Assay min % | 95% (by chemical analysis) |
| Acid value max | 5.0 |
| Refractive index | 1.527-1.534 |
| Specific gravity | 0.973-0.981 |
| Other requirements | (equivalence factor for assay = 74.04) |
| ID Test | IR |
| Spectrum | http://www.fao.org/ag/agn/jecfa-flav/img/img/868.gif |
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