Functional Group Chemistry 2

Question 1

Describe alkanes

Answer 1

Saturated = single bonds = sigma
CnH2n+2
pKa > 50

Question 2

What are the properties of alkanes?

Answer 2

Poorly reactive with ionic or polar substances
Inert to acids + bases
Virtually insoluble to H2O

Question 3

What happens to boiling point as size of alkanes increase?

Answer 3

Increase

Question 4

What are alkanes used for?

Answer 4

Fuels

Question 5

Describe intermolecular forces of alkanes

Answer 5

Weak = no difference in electronegativity = no dipoles

Question 6

Describe alkenes

Answer 6

Unsaturated = pi bonds
Double bond = slightly polar
CnH2n

Question 7

What is reactivity controlled by in alkenes?

Answer 7

How e- rich the double bond is = act as nucleophile

Question 8

What does it mean the pi bond in alkenes is polarizable?

Answer 8

= instantaneous dipole-dipole interactions occur

Question 9

What do the conversion of alkene isomers require?

Answer 9

Breaking of pi bond between 2x sp2 carbons

Question 10

How do you get from alkene cis to trans?

Answer 10

180 degrees

UV light

Question 11

What is cis?

Answer 11

Same side

Question 12

What is trans?

Answer 12

Opposite

Question 13

What happens when C=C is broken to C-C?

ISOMERS

Answer 13

C=C reformed to form more stable orbitals

Question 14

What is the preparation methods for alkenes?

Answer 14

Cracking

Elimination reactions of halides/alcohols

Question 15

What can alkenes form?

Answer 15

Haloalkanes
Alcohols
Vicinal dihaloalkanes
Alkanes
Polymers

Question 16

What is addition reactions via for alkenes?

Answer 16

Electrophilic addition

Question 17

Where does e- move in alkenes?

Answer 17

From double bond to electrophilic centre

Question 18

What can addition reactions be?

Answer 18

Homolytic (involves radicals)

Heterolytic (involves cations)

Question 19

Describe reactivity of C=C

Answer 19

Pi e- attack E+ (heterolytic) or radical intermediate (homolytic)
Nu- adds to carbocation/radical

Question 20

Describe addition of halogens to alkenes

Answer 20

Cl2, Br2 + I2 add to C=C to form vicinal dihalide

Anti or trans addition = stereospecific reaction

Question 21

Describe addition of bromine to alkenes

Answer 21

Red/brown colour goes colourless upon reaction

Br- = Nu-

Question 22

Describe addition of H-X to alkenes

Answer 22

Symmetrical alkene = 1 product

Unsymmetrical = 2 different products

Question 23

Describe anti-Markovnikov addition to alkenes

Answer 23

Peroxides present = HBr adds to alkenes to form “Anti-Markovnikov” product through radical mechanism
Only HBr has right bond energy

Question 24

Describe anti-Markovnikov addition to alkenes stages

Answer 24

Initiation + propagation = Br2 adds to sterically least hindered C
Radical cleaves HBr in 2nd propagation
= radical chain
Termination = contamination

Question 25

Describe hydrogenation in alkenes

Answer 25

Form alkane Syn or Cis addition Reaction = stereospecific Catalyst required = Pt, Pd or Ni

Question 26

Describe alkynes

Answer 26

``` Unsaturated Triple bonds Reactivity dominated by reactive e- rich triple bond CnH2n-2 pKa = 44 ```

Question 27

What are the properties of alkynes?

Answer 27

Virtually insoluble to H2O Stronger Van Der Waals Internal alkenes/alkynes have higher boiling points than terminal

Question 28

Describe electronegativity of orbitals

Answer 28

sp > sp2> sp3 sp = most sp3 = least

Question 29

What happens to acidity as s-orbital character increases?

Answer 29

Increases

Question 30

Describe alkyne reactivity

Answer 30

Completely burn in O2

Question 31

What reactions do alkyne undergo?

Answer 31

``` H-X addition With/without peroxides X-X addition (Br2, Cl2) Hydrogenation H-OH (hydration) Alkylation of terminal alkynes ```

Question 32

Describe addition of HX to alkynes

Answer 32

Follows Markovnikov rule Vinylic carbocations in 1st step Triple bond compose of sigma bond + 2x pi bonds Pi bond broken = new sigma bonds formed 2nd addition

Question 33

What are the alkyne addition reaction?

Answer 33

``` Halogenation = same as alkenes Anti-Markovnikov = needs peroxide ```

Question 34

Describe addition of H2O to alkynes

Answer 34

Same as alkenes | Acid catalysed