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Nucleophilic substitution rates and solubilities for methyl halides in seawater
Author(s) -
Elliott Scott,
Rowland F. Sherwood
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl01081
Subject(s) - seawater , halide , bromide , solubility , halogen , distilled water , dimensionless quantity , reaction rate constant , aqueous solution , chemistry , chloride , nucleophile , inorganic chemistry , henry's law , thermodynamics , organic chemistry , alkyl , geology , oceanography , catalysis , kinetics , physics , chromatography , quantum mechanics
Ozone depletion potentials indicate that methyl bromide is among halogen containing gases which may be scheduled for international level regulation. The oceanic component of its global budget is currently unquantifiable because of a lack of surface seawater measurements. Given values for internal removal and for solubility, marine mixed layer modelling can set bounds for air‐sea transfer. Rate constants have been measured in seawater, 0.5m NaCl and distilled water for attack on methyl bromide by the chief oceanic nucleophiles chloride ion and H 2 O, over much of the oceanographic temperature range (0°C to 22°C). Henry's Law constants have been determined for the same conditions. All results are consistent with classical aqueous phase research adjusted for ionic strength effects. The lifetime of methyl bromide with respect to chemical decay in seawater is three weeks at average surface temperatures, and a factor of ten larger and smaller at the extremes. Its dimensionless solubility ranges from 0.1 to 0.3. Analogous experiments are reported for the other natural methyl halides, CH 3 Cl and CH 3 I.