5. The SN2 reaction is one of the most important reactions covered in Chem 2400. Which of the following statements about this reaction are true? the optimal orientation for the approach of the nucleophile to the alkyl halide is from the front side of the C-X bond. ⚫the optimal orientation for the approach of the nucleophile to the alkyl halide is from the back side of the C-X bond. ⚫ the order of reactivity with regard to the alkyl halide is CH₂ > 1*> 2* > 3*. ⚫ the order of reactivity with regard to the alkyl halide is 3* > 2* > 1* > CH₂. ⚫for secondary alkyl halides, there is often competition between S₁2 and E2 reactions. ⚫ for chiral secondary alkyl halides, the configuration of the stereogenic centre is inverted. neopentyl halides react nicely in SN2 reactions because they are primary. • "Sn₂" refers to an as-yet undiscovered form of elemental tin and not an organic reaction.

Which reagent can be used to convert ethanol (a poor nucleophile) into an alkoxide (a good nucleophile), which can then be used in an SN2 reaction to make a new O-C bond? Reagent Br Good HO, Nucleophile SN2 А. NaH В. HOC(CH3)3 · NaCl D.H20

The mechanism proceeds through a first cationic intermediate, intermediate 1. Nucleophilic attack leads to intermediate 2, which goes on to form the final product. In cases that involve negatively charged nucleophile, the attack of the nucleophile leads directly to the product. H. Br + CH3OH Br Intermediate 2 (product) Intermediate 1 In a similar fashion, draw intermediate 1 and intermediate 2 (final product) for the following reaction. OCH3 Cl2 MEOH ĆI racemic mixture Pay attention to the reactants, they may differ from the examples. In some reactions, one part of the molecule acts as the nucleophile. • You do not have to consider stereochemistry. • Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner. Separate intermediate 1 and intermediate 2 using the the dropdown menu. → symbol from

A 3. Rank the following compounds in terms of reactivity with a good nucleophile. Br B NH₂ F D OH E CI

9. Rank the following nucleophiles, in a solution of DMF, in order of weakest to strongest. НО CI Strong Br Slow II II IV

#18.        I need help in part 5

Which of these would be the best nucleophile?

0 0 B What is the strongest nucleophile in this list? B OH D

4. A CHEM 245 student wants to synthesize some ethylene glycol to use as antifreeze in his radiator this winter. He proposes the following reaction to his instructor, who quickly explains that this reaction won't work as proposed due to the student's choice of reagent. 1) NaH 2) H20 OH Но a) Why can't sodium hydride (NaH) be used as the nucleophile in the reaction above? b) Propose an alternate reagent that COULD be used with the ethylene oxide to successfully give the desired ethylene glycol product.

OH OH ∞∞ BF3 Et₂O This reaction takes place via a pinacol rerrangement. Please, draw curved arrows to show the movement of electrons in this SPECIFIC step of the reaction mechanism. +BF3 HO: :OH OH (BF3OH)