Exam 3 Notes

Exam 3 Notes - Nucleophiles: o They are Lewis bases. o They...

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- Nucleophiles: o They are Lewis bases. o They react with electrophiles at electron-deficient atoms. o They donate an electron pair to the electrophile to form a new covalent bond. o Most have an unshared electron pair that is donated to the electrophile. - Across a periodic table row, nucleophilicity and basicity increase from right to left, because the less electronegative an atom is, the more readily it donates an electron pair. - Within one column of the periodic table, nucleophilicity increases in the downward direction, opposite to the trend of basicity. - A conjugate base is always a stronger nucleophile than the acid. - A base is always a stronger nucleophile than its conjugate base. - The faster a nucleophile reacts with an electrophile, the stronger the nucleophile is. - Solvents affect nucleophilicity. - Solvation : the solvent-solute interaction. - Protic solvents have O-H or N-H bonds (ex: water, ethanol, formamide, ethanoic (acetic) acid). They solvate nucleophiles by hydrogen bonding, lowering their nucleophilicity. - Aprotic solvents have no O-H or N-H bonds (ex: acetonitrile, 2-propanone (acetone), tetrahydrofuran (THF), toluene) - Protic solvents solvate nucleophiles by forming hydrogen bonds to their nucleophilic atoms.
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This note was uploaded on 03/21/2008 for the course CHEM 261 taught by Professor Austell during the Spring '08 term at UNC.

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Exam 3 Notes - Nucleophiles: o They are Lewis bases. o They...

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