Why does fresh fish remind us the smell of sea air?
One of the characteristics of a fresh saltwater fish is its distinctive smell of seacoast air. Why is that?
The Ocean aroma of the seacoast comes from compounds called bromophenols*. These molecules are synthesised by algae and some primitive animals from bromine* ; an abundant sea water element. Present in sea water, bromophenols are propelled into the seacoast air by the actions of the waves and the spray, where we smell them directly.
Wild saltwater fish also store bromophenols either by eating algae or algae eaters. This is how the aroma of fish remind us the seacoast air.
On the other hand, farmed saltwater fish can lack of this aroma because fish feed doesn't contain any bromophenols. Nowadays, some fish farmers supplement the their artificial feed with these compounds, but nothing is worth the "real mac coy".
Bromine
Atomic number : 35
Atomic mass : 79.904 g.mol -1
Electronegativity according to Pauling : 2.8
Density : 3.1 g.cm-3 at 20°C
Melting point : - 7.2 °C
Boiling point : 58.8 °C
Vanderwaals radius : 0.165 nm
Ionic radius : 0.195 nm (-1)
Isotopes : 10
Electronic shell : [ Ar ] 3d10 4s2 4p5
Energy of first ionisation : 1142.7 kJ.mol -1
Standard potential : 1.08 V
Discovered by Anthoine Balard in 1826
Bromophenols
The complete series of 19 bromophenols have been studied by density functional theory (DFT) calculations at the B3LYP/6-311G++(d,p) level. The molecular structures and properties of bromophenols are strongly influenced byintramolecular hydrogen bonding of ortho-bromine, steric and inductive effects of substituted bromine, and other intramolecular electrostatic interactions. Systematic trends in several structural parameters and molecular properties of bromophenols have been found with the increasing number of bromine substitutions, including increase in O-H bond length, decrease in C-O bond length, red shift in O-H stretching frequency, and blue shift in O-H torsional frequency. Correlations among several key molecular parameters as well as those with available aqueous pK[a] values are examined. Comparisons with chlorophenols have indicated that the inductive effect of substituted bromine appears larger and bromophenols are slightly stronger acids than chlorophenols.
Copyright 2006 INIST-CNRS. All rights reserved
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