SN1 reaction conditions: To create reaction conditions for an SN1 reaction, silv

Question

SN1 reaction conditions: To create reaction conditions for an SN1 reaction, silver nitrate in an ethanol solution will be utilized. The silver cation (Ag+), from the silver nitrate ionic compound, coordinates with one of the lone electron pairs of the halogen, facilitating the departing of the leaving group, i.e. the halide ion. The parting halide forms an insoluble ionic compound with the Ag+, forming a precipitate, while promoting the formation of a carbocation. Ethanol is a polar, protic solvent and as such will promote ionization of the alkyl halide and stabilize the forming carbocation. Since SN1

SN2

Bimolecular, single step, 2° order

Alkyl Halide

1° > 2° > 3°

Stereochemistry:

Inversion

Solvent: polar, aprotic

SN1

Unimolecular, two steps, 1° order

Alkyl Halide

3° > 2° > 1°

Stereochemistry:

Racemization

Solvent: polar, protic or aprotic

2

reactions also called solvolysis reactions, ethanol will also serve as a weak nucleophile carrying out the attack on the carbocation intermediates.

SN2 reaction conditions: To create reaction conditions suitable for an SN2 reaction, sodium iodide will be employed. Iodide is a great nucleophile, which works the best in an aprotic solvent, thus acetone will be utilized for these reactions. As a side product, the sodium cation will form an ionic compound with the leaving halides. Since sodium chloride and sodium bromide is not soluble in acetone, thus the successful substitution reaction of the halides will be confirmed visually by the formation of a salt precipitate.

Experimental goal:

1, Test all available halides under both SN1 and SN2 conditions. Determine which halide is more susceptible to undergo which mechanism.

Table 2 indicates the available halides. NAME STRUCTURE Participates in SN1 Participates in SN2

1 1-bromobutane Br

2 Bromobenzene Br

3 2-bromobutane Br

4 1-chlorobutane Cl

5 1-chloroadamantane Cl

6 3-chloro-1-butene CH3 CH 2 Cl

7 1-chloro-2- methylpropane Cl

8 2-chloro-2- methylpropane Cl

9 iodoethane I CH3

Explanation / Answer

1: 1 - bromobutane is a 1 degree alkyl halide. Hence it undergoes SN2 reaction.

2: Bromobenzene doesn't undergo either SN1 or SN2 reaction.

3: SN1 reaction is more favorable for 2-bromobutane.

4: Since 1-chlorobutane is a 1 degree halide, it undergoes SN2 reaction.

5: Since 1-chloroadamantane is 3 degree alkyl halide, it undergoes SN1 reaction.

6: Allyl carbocation is formed by 3-chloro-1-butene after the removal of bromide ion. Since the allyl carbocation formed is resonance stabilized it undergoes SN1 reaction.

7: Since 1-chloro-2- methylpropane is a 1 degree halide, it undergoes SN2 reaction.

8: 2-chloro-2- methylpropane is a 2 degree halide and SN1 reaction is more favored.

9: Since iodoethane is a 1 degree halide, it undergoes SN2 reaction.

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