CHEM 330 Exam 3
1. What are four possible options for substitution and elimination reactions?-
: -SN1
-SN2
-E1
-E2
2. If its a methyl, what reaction is it?: SN2 (only if Nu/Base is strong & strong, or strong and weak). If not, then no
rxn occurs
3. If Nu/base is strong & strong, what type of reaction is it?: -methyl: SN2
-primary: SN2
-secondary: E2
-tertiary: E2
4. If Nu/base is strong & weak, what type of reaction is it?: -methyl: SN2
-primary: SN2
-secondary: SN2
-tertiary: No rxn
5. If Nu/base is weak & strong, what type of reaction is it?: -methyl: No rxn
-primary: E2
-secondary: E2
-tertiary: E2
6. If the Nu/base is weak & weak, what type of reaction is it?: -methyl: no rxn
-primary: no rxn
-secondary: SN1/E1
-tertiary: SN1/E1
7. What are organohalides?: -Organic molecules that contain one or more halogen atom bonded to a C atom
-Halogens are in group 17
-many cl, br, and I, occur naturally, but organofluroides are very rare in nature
-Halogen atom can be bonded to any type of C (SP3, SP2, or SP)
8. How do you name alkyl halides with IUPAC?: -treat the halogen as a sub- stituent
F= fluoro Cl=
Chloro Br=
Bromo I= Iodo
-The parent chain (methane, propane, butane, etc) will end in "ane"
-Can use prefixes if there are more than one of that halogen
-Halogen name goes in very front of other substituents
, CHEM 330 Exam 3
9. What is a substitution reaction?: -an atom or group bonded to a carbon is replaced by another atom or group
-in a nucleophilic substitution reaction, the entering group is the *nucleophile*
10.What is a substrate?: -The organic molecule at which the reaction is occurring
-alkyl halides are the substrates in this topic
11.What is the leaving group?: -The group that is replaced during substitution
12.What are the charges of nucleophiles?: -Can be anions or neutral
-For neutral nucleophiles, the nucleophilic atom will acquire a formal positive charge in the product
13.What is Nucleophilicity?: -The ability of the nucleophile to displace the leaving group from the substrate
-In other words: how readily the nucleophile forms a bond with the partially positively charged C atom
14.What 4 things matter when comparing nucleophile strength?: -Charge/ lone pairs
-Resonance
-Down group & across period effects
-Overall size & shape
15.When comparing nucleophiles, how does charge & lone pairs work?: -neu- tral nucleophile = acid
-anion nucleophile = conjugate base
-Molecule with more lone pairs = stronger Nu
-Molecule with neg. charge = stronger Nu
-*Acid < conjugate base*
16.When comparing nucleophiles, how does resonance work?: -*Better Nu = no resonance*
-No resonance means the neg. charge is concentrated more on a single atom
-resonance means neg charge is stabilized by being spread over 2 atoms
17.When comparing nucleophiles, how does the first periodic trend work? (down group): -an element farther
down the group is a better nucleophile
Ex. OH < HS
-Element gets bigger down the group
-Polarizability: ability to distort e- cloud, easier for larger ions
18.When comparing nucleophiles, how does the second periodic trend work? (across period): -Element to left is
better nuclephile (when in same row)
Ex. CH3 > NH2
-Least electronegative is a better Nu
, CHEM 330 Exam 3
-Least electronegative is strong base
-Least electronegative is worst at stability
19.When comparing nucleophiles, how does overall size and shape work?: -
-best Nu is one with less groups attached to nucleophile Ex. OH > Ch3-O
-The less steric hinderance the better the Nu
20.What is steric hinderance?: -size of Nu prevents it from approaching substrate closely
-Nu uses a back attack
21.For halides, which is a poor and good leaving group? (trend): F- << Cl- < Br- < I-
F is a very poor leaving group I is a very
good leaving group
Trend correlates with basicity. I is weakest base and F is strongest base
22.Are some groups only good leaving groups when pronated?: -Yes
-Ex. Lone pairs on O in alcohol attack H+. Turns into a water with positive charged O, now making it a good leaving
group
23.What are the two mechanisms possible for nucleophilic substitution?: -
-SN2
-SN1
24.What do the names SN1 and SN2 mean?: S = substitution N = nucleophilic
1 & 2 = refer to number of species involved in rate determining step (the slow step)
25.For SN2, what determines the rate determining step?: -Both the nucleophile and the substrate
26.Rate equation for SN2: Rate = K[Nu]x[Substrate/E]
27.What does K mean?: Its the rate constant
28.How does an SN2 mechanism work?: 1. Nu attacks substrate, causes leaving group to leave and Nu attaches
2. Leaving group is left by itself
-takes place in one step
29.3 facts about SN2:: -Rxn occurs in 1 elementary step (called a concerted rxn mechanism)
-Rate depends conc. of both Nu and substrate
-Rate of rxn is dependent on structure of substrate
30.What is a concerted reaction mechanism?: -All bonds are made/broken at the same time
1. What are four possible options for substitution and elimination reactions?-
: -SN1
-SN2
-E1
-E2
2. If its a methyl, what reaction is it?: SN2 (only if Nu/Base is strong & strong, or strong and weak). If not, then no
rxn occurs
3. If Nu/base is strong & strong, what type of reaction is it?: -methyl: SN2
-primary: SN2
-secondary: E2
-tertiary: E2
4. If Nu/base is strong & weak, what type of reaction is it?: -methyl: SN2
-primary: SN2
-secondary: SN2
-tertiary: No rxn
5. If Nu/base is weak & strong, what type of reaction is it?: -methyl: No rxn
-primary: E2
-secondary: E2
-tertiary: E2
6. If the Nu/base is weak & weak, what type of reaction is it?: -methyl: no rxn
-primary: no rxn
-secondary: SN1/E1
-tertiary: SN1/E1
7. What are organohalides?: -Organic molecules that contain one or more halogen atom bonded to a C atom
-Halogens are in group 17
-many cl, br, and I, occur naturally, but organofluroides are very rare in nature
-Halogen atom can be bonded to any type of C (SP3, SP2, or SP)
8. How do you name alkyl halides with IUPAC?: -treat the halogen as a sub- stituent
F= fluoro Cl=
Chloro Br=
Bromo I= Iodo
-The parent chain (methane, propane, butane, etc) will end in "ane"
-Can use prefixes if there are more than one of that halogen
-Halogen name goes in very front of other substituents
, CHEM 330 Exam 3
9. What is a substitution reaction?: -an atom or group bonded to a carbon is replaced by another atom or group
-in a nucleophilic substitution reaction, the entering group is the *nucleophile*
10.What is a substrate?: -The organic molecule at which the reaction is occurring
-alkyl halides are the substrates in this topic
11.What is the leaving group?: -The group that is replaced during substitution
12.What are the charges of nucleophiles?: -Can be anions or neutral
-For neutral nucleophiles, the nucleophilic atom will acquire a formal positive charge in the product
13.What is Nucleophilicity?: -The ability of the nucleophile to displace the leaving group from the substrate
-In other words: how readily the nucleophile forms a bond with the partially positively charged C atom
14.What 4 things matter when comparing nucleophile strength?: -Charge/ lone pairs
-Resonance
-Down group & across period effects
-Overall size & shape
15.When comparing nucleophiles, how does charge & lone pairs work?: -neu- tral nucleophile = acid
-anion nucleophile = conjugate base
-Molecule with more lone pairs = stronger Nu
-Molecule with neg. charge = stronger Nu
-*Acid < conjugate base*
16.When comparing nucleophiles, how does resonance work?: -*Better Nu = no resonance*
-No resonance means the neg. charge is concentrated more on a single atom
-resonance means neg charge is stabilized by being spread over 2 atoms
17.When comparing nucleophiles, how does the first periodic trend work? (down group): -an element farther
down the group is a better nucleophile
Ex. OH < HS
-Element gets bigger down the group
-Polarizability: ability to distort e- cloud, easier for larger ions
18.When comparing nucleophiles, how does the second periodic trend work? (across period): -Element to left is
better nuclephile (when in same row)
Ex. CH3 > NH2
-Least electronegative is a better Nu
, CHEM 330 Exam 3
-Least electronegative is strong base
-Least electronegative is worst at stability
19.When comparing nucleophiles, how does overall size and shape work?: -
-best Nu is one with less groups attached to nucleophile Ex. OH > Ch3-O
-The less steric hinderance the better the Nu
20.What is steric hinderance?: -size of Nu prevents it from approaching substrate closely
-Nu uses a back attack
21.For halides, which is a poor and good leaving group? (trend): F- << Cl- < Br- < I-
F is a very poor leaving group I is a very
good leaving group
Trend correlates with basicity. I is weakest base and F is strongest base
22.Are some groups only good leaving groups when pronated?: -Yes
-Ex. Lone pairs on O in alcohol attack H+. Turns into a water with positive charged O, now making it a good leaving
group
23.What are the two mechanisms possible for nucleophilic substitution?: -
-SN2
-SN1
24.What do the names SN1 and SN2 mean?: S = substitution N = nucleophilic
1 & 2 = refer to number of species involved in rate determining step (the slow step)
25.For SN2, what determines the rate determining step?: -Both the nucleophile and the substrate
26.Rate equation for SN2: Rate = K[Nu]x[Substrate/E]
27.What does K mean?: Its the rate constant
28.How does an SN2 mechanism work?: 1. Nu attacks substrate, causes leaving group to leave and Nu attaches
2. Leaving group is left by itself
-takes place in one step
29.3 facts about SN2:: -Rxn occurs in 1 elementary step (called a concerted rxn mechanism)
-Rate depends conc. of both Nu and substrate
-Rate of rxn is dependent on structure of substrate
30.What is a concerted reaction mechanism?: -All bonds are made/broken at the same time
