Relative nucleophilicity of bromide? (Put a brief statement of your accomplishme
ID: 1049663 • Letter: R
Question
Relative nucleophilicity of bromide? (Put a brief statement of your accomplishments here.) Reaction Data Volume of 1-butanol Mass of 1-butanol Moles of 1-butanol Theoretical yield of total alkyl halide product (mol) Actual yield of total alkyl halide products (g) GC Analysis Retention time of 1-chlorobutane Retention time of 1-bromobutane Area under 1-chlorobutane peak Area under 1-bromobutane peak Percent 1-chlorobutane in mixture Percent 1-bromobutane in mixture Relative nucleophilicity of chloride Relative nucleophilicity of bromide Do your results make sense? Explain. Describe how the following procedural variations would affect the observed product ratio? Concentrated H_2SO_4 and 1-butanol were added before oil of the salts dissolved Some of the product escaped during reflux or evaporated during work-up Are there any inherent problems with the design of the competition that would render the observed relative nucleophilicities inaccurate?Explanation / Answer
The nucleophilicity is the tendency of a Lewis base to attack the electron deficit carbon of organic molecule.
The nucleophilicity of halide ions varies with the solvent used.
In non-polar solvents or in gaseous phase reactions, the nucleophilicity of halides is proportional to their basicity.
order of basicity and nucleophilicity i gas phase is
F- > Cl- . Br- > I-
However the nucleophilicity of the halides in polar protic solvents is different. In polar protic solvents , the anion is solvated . The smaller the anion, more is the solvation, thus its approach towards carbon becomes less easy. Thus the nucleophilicity and basicity are not parallel in polar protic solvents like water, ethanol, acetic acid or formic acid.
The order of basicity does not change that is F-> Cl- > Br - > I-
but the order of nucleopilicity is reverse that is I- > Br-> Cl- > F-
Again in polar aprotic solvents like DMf, DMSO, HMPA the cations( posive ions) only are solvated and the anions(Lewis bases) are not solvated (no H in solvent that arepolar).Thus the nucleophilicity follows basicity.