FINAL - Chapter 7 Organic Reactions

Question 1

Distinguish between (strong) nucleophile and (strong) electrophile

Answer 1

Nucleophile : excess negative charge, affinity for positive charge, strong nucleophiles are electron rich

Donates

Electrophile: Excess positive charge, affinity for negative charge
Strong Electrophile: e- poor, incomplete valence, or large partial positive charge

Accepts

Question 2

Outline nucleophilic substitution in one sentence

Answer 2

Leaving group replaced by electrophile

R-Lg + Nu: = R-Nu + Lg:

Question 3

What is unimolecular? How about bimolecular?

Answer 3

Unimolecular: One particle participating in elementary step

Bimolecular: One particle participating in elementary step

Question 4

SN2 Reaction (concerted)

What types of electrophiles is it for (and not for?

What are factors that increase the rate? (x4)

Answer 4

Mostly for methyl or primary halogenoalkane, slow for secondary.

Not for tertiary for aromtic ring

Less substituted electrophile
Strong nucleophile (more negatively charged)
Good leaving group (less BDE, so i faster than Br faster than Cl)
Polar aprotic solvent (has dipole, but cannot H bond, like amides and ketones)

Question 5

Sn1 Reaction (stepwise)

What types of electrophiles is it for

What are factors that increase the rate? (x4)

Answer 5

Tertiary

More substituted electrophile
Nucleophile has no effect (so less substituted is more suited to SN1 because more substituted is suited to SN2
Good LG
Polar, protic solvent (like water, alochols, carboxylic acids)

Question 6

What happens if stereocenter is chiral in SN2 and SN1

Answer 6

In SN2, it inverts sterocenter

In SN1, it can create racemic mixture (not always, but chirality is requied to even consider racemic)
Racemic mixture: 50/50 R and S.
Each enantiomer is optically active but mixture isn’t because rotations cancel