Chapter 10-Organic Chem

Question 1

SN1 Unimolecular or Bimolecular?

Answer 1

Unimolecular = only 1 species involved in RDS

Question 2

Mechanism of SN1 (2)

Answer 2

1) Heterolytic fission of C-X bond to produce = acts an an intermediate (RDS)
2) Carboncation reacts rapidly w/ hydroxide ion to yield final product

Question 3

Hydrolysis of Halogenoalkanes to Alcohol: mechanism + conditions

Answer 3

R-X + H2O → R-OH + HX
+ Heat under reflux w/ sodium or potassium hydroxide
+ Solvent of 50/50 water and ethanol
→ Cuz halogenoalkane insoluble in water

Question 4

SN2 Unimolecular of Bimolecular?

Answer 4

Bimolecular = 2 species affecting the RDS

→ Halogenoalkane and the nucleophile

Question 5

SN1 and SN2 which one is primary and which one tertiary?

Answer 5

SN1 = Tertiary (big and bulky so needs 2 step process)
SN2 = Primary (smaller, less stable so one step process is OK)

Question 6

SN2 RDS?

Answer 6

Attack of hydroxide ion on the halogenoalkane

Question 7

SN2 transition state?

Answer 7

When the bond to Nu- starts to form at the same time as the bond to X broken!

Question 8

Halogenoalkanes exists as what type of isomers?

Answer 8

Stereoisomers because there are 4 different groups attached to the carbon atom (w/ the Halogen)

Question 9

Halogenoalkanes can exist as?

Answer 9

A pair of enantiomers

Question 10

SN2 → start with one PURE enantiomer what is the product?

Answer 10

PURE enantiomer with inverted configuration

Question 11

SN1 what type of carboncation formed?

Answer 11

Planar carboncation intermediate

→ Nu- can attack on either side of it

Question 12

What mixture does SN1 mechanism result in?

Answer 12

Racemic mixture

= cuz there are EQUAL prob. of both attacks of the Nu-

Question 13

Which mechanism does secondary halogenoalkanes use?

Answer 13

Both SN1 and SN2

Question 14

How does the nature of the X also affects the mechanism choice? (2)

Answer 14

1) Polarity of the C-X bond
→ decreases from Cl to I = decreases the susceptibility of the C to a SN2 attack cuz the partial + charge on the C would be smaller
2) Strength of the C-X bond
→ decrease from Cl to I = so the bonds in the 1st step of SN1 breaks more easily w/ I

Question 15

Which Halogen does SN1 and SN2 prefer?

Answer 15

SN1 = Iodine
SN2 = Chlorine
Bromine = both mechanisms can occur

Question 16

Solvents that SN1 prefers?

Answer 16

+ Polar s.a water and alcohol
→ cuz they can solvate the ions formed by heterolytic fission
+ Protic = can H.bond cuz they contain a H bonded to and O or N → they often bind to nucleophiles making SN2 less favourable.

Question 17

Solvents that SN2 prefers?

Answer 17

+ Polar = so that solvent can bond to leaving group and it can dissolve in them
+ Aprotic
→ so don’t solvate nucleophile

Question 18

Which reaction occurs faster SN1 or 2

Answer 18

SN1 is faster!

→ so factors that favour SN1 tend to increase the rate of reaction

Question 19

What species undergo Electrophilic addition reactions and how many steps is it?

Answer 19

+ Alkenes

+ 2 step process

Question 20

What do Electrophiles act as?

Answer 20

+ Lewis Acids = electron pair acceptor
+ attacks region of high electron density
→ double bonds or triple bonds

Question 21

What are Electrophiles?

Answer 21

Electron deficient species = Electron LOVIN’ <3

→ Either has a formal + charge or has a partial + charge due to the presence of highly electronegative specie.

Question 22

Examples of non-symmetrical electrophiles (2)

Answer 22

H-Br / I-Cl

Question 23

Which one attacks the Alkene in a non-symmetrical electrophile?

Answer 23

The one with the more + charge = the one with the less electronegativity

Question 24

List the carboncations in order of stability (more stable first):
Secondary
Primary
Tertiary

Answer 24

Tertiary (most stable) > Secondary > Primary

Question 25

What makes a carboncation species more stable?

Answer 25

The lower the electrical charge on the C atom

Question 26

Inductive effect

Answer 26

The effect of a funct. group or atom in an organic molecule in attracting (sigma electrons) towards itself OR repelling them
→ results in the formation of a dipole molecule

Question 27

When an electrophile attacks a non-symmetrical alkene which carboncation predominates leading to the major product?

Answer 27

The more stable one

Question 28

Markovnikov’s Rule? →

used to predict the Maj. product of the Electrophilic addition of hydrogen Halides (H-X) to unsymmetrical alkenes

Answer 28

“Hydrogen atoms will preferentially bond to the C atom of the alkene already has most hydrogens attached to it in a double bond”

Question 29

Reduction reactions depend on what?

Answer 29

Reagents that can donate a hydride ion (H-) to a molecule