Alkanes

Question 1

What’s syn addition ?

Answer 1

If during addition reaction of an alkene the groups are attached on the same side it’s called syn addition.

Question 2

What’s anti addition ?

Answer 2

If during addition reaction the groups are attached on the opposite direction then the addition is called anti addition.

Question 3

In case of catalytic addition of H2 what kind of addition takes place ?

Answer 3

Syn addition

Question 4

If the Alkane is unsymmetrical , then it forms what kind of mixture in addition ?

Answer 4

Racemic mixture , irrespective of syn or anti.

Question 5

What does Red phosphorous and HI do when they act as catalyst to alchols and compounds containing C=O ?

Answer 5

Red phosphorus and HI reduces them to Alkane

Question 6

With 1 degree halide , LiAlH4 reacts with which mechanism to form Alkane? What about NaBH4?

Answer 6

With 1 degree halide , LiAlH4 reacts in SN2 mechanism to form Alkane and NaBH4 does not undergo any reaction.

Question 7

With 2 degree alkyl halide , LiAlH4 reacts with which mechanism to form Alkane? What about NaBH4?

Answer 7

LiAlH4 undergoes SN2 mechanism whereas NaBH4 undergoes SN1 mechanism through carbocation formation of hallide.

Question 8

With 3 alkyl degree halide , LiAlH4 reacts with which mechanism to form Alkane? What about NaBH4?

Answer 8

LiBH4 will act as a base with 3 degree hallide through elimination reaction whereas NaBH4 will proceed through SN1 mechanism.

Question 9

Catalytic Hydrogenation Reaction of Alkenes

Answer 9

CH3-CH=CH2–(H2,Pt/Pd/Ni)–> CH3-CH2-CH2.

Energy released during chemisorption is more than energy to break H-H bonds.

Question 10

Sabatier Sandern’s reaction CnH2n—>?

Answer 10

CnH2n/CnH2n-2—H2,Ni/573K——->CnH2n+2

Question 11

Alkane preparation by alkene reduction

Answer 11

(CH₃)₂-C=CH₂—Pd-C/C₂H₅OH—> (CH₃)₂CHCH₃

Question 12

Alkane preparation by alkyl halide reduction

Answer 12

RX + H2–RA–>RH + HX
; X = Halogen
RA= Zn + CH3COOH/ Zn+ HCl

Question 13

Wurtz Reaction for alkanes

Answer 13

2RI+Na–dry ether–>R-R+NaI

Question 14

Alkane preparation by alkyl iodide reduction

Answer 14

RI+HI–Red Phosphorous/150 C–>RH-I2

Question 15

Frankland Reaction ( Alkanes )

Answer 15

RI+Zn+RI—->RR+ZnI2

Question 16

Alkane preparation by alcohol reduction

Answer 16

ROH+2HI–Red Phosphorous,150 C–>RH+I2+H2O

Question 17

Clemmension’s Reaction for Alkanes

Answer 17

RCHO+2H2–(Zn-Hg),HCl–>RCH3+ H20

Question 18

Alkane preparation by carboxylic acid reduction

Answer 18

RCOOH+6HI–Red Phosphorous–>RCH3+2H20+3I2

Question 19

Decarboxylation reaction ( Alkane )

Answer 19

RCOONa+ NaOH–CaO,heat–>RH+ Na2CO3

Question 20

Kolbe’s Electrolysis ( Alkanes )

Answer 20

2CH3COONa+ H20–electrolysis–>CH3-CH3+ CO2 + 2NaOH + H2
; At anode = CH3-CH3+CO2
At cathode = H2

Question 21

Alkane preparation by Aluminium Carbide

Answer 21

Al₄C₃+12H₂0—->3CH₄+4Al(OH)₃

Question 22

Alkane preparation by beryllium carbide

Answer 22

Be2C+H20—->CH4+2Be(OH)2

Question 23

Corey House Synthesis

Answer 23

RX+2Li–diethyl ether–>RLi+LiX–diethyl ether–R2CuLi+LiI—->R-R’+RCu+LiX

Question 24

Swartz Reaction (Alkanes)

Answer 24

2CH₃CH₂-Cl+Hg₂F₂—->2CH₃CH₂F+Hg₂Cl₂

Question 25

Halogenation of Alkane

Answer 25

CH4–Cl2/hv–>CH3Cl–Cl2/hv–>CH2Cl2–Cl2/hv–>CH3Cl–Cl/hv–>CCl4

Question 26

Order of ease of Halogenation

Answer 26

3⁰RX->2⁰RX->1⁰RX->CH₄