Organic

Question 1

alkynes general formula

Answer 1

CnH2-2

Question 2

reactivity of alkanes, alkenes and alkynes.

Answer 2

Alkene>Alkyne>Alkane.

.alkene has electrons more exposed for attack
.pi bond is weak

.alkyne short bondlength

.alkane have inert sigma bonds and is nonionic.

Question 3

paraffins also known as?

Answer 3

alkanes

Question 4

preparation of alkynes(2 methods)

Answer 4

1.Dehydrohalogenation of Vicinal dihalide (R-C2H2X2-R) {elimination}

2. Dehalogenation of Tetrahalides [zn metal used]

Question 5

alkynes addition reactions

Answer 5

1.hydrogenation [ni/pt]
“triple bond to c=c then c-c”

2.hydrohalogenation [addition of hx]
“ethyne turns into vinyl bromide and then 1,1 dibromoethane”

3.hydration [HgSO4/H2SO4]
“ethyne gives acetaldehyde. rest give ketones”

Question 6

acidic nature of alkynes used to distinguish bw

Answer 6

used to distinguish between
.alkynes and alkenes
.Terminal alkyne from other alkynes

Question 7

ethyne reaction with sodamide [NaNH2] in liq. NH3 (ammonia).

Answer 7

Formation of Sodium acetylide(used for chemical synthesis)

R-C—CH + NaNH2—–liq NH3——->R-C—CNa +NH3

HC—CH + 2Na—–> NaC—Cna + H2
[sodium acetylide]

Question 8

how acetylides of copper and silver obtained?

Answer 8

passing acetylene (C2H2) in ammonical sol of cuprous chloride (Cu2Cl2) and THEN silver nitrate solution (NH4OH)

Question 9

phenol reactions due to -OH group

Answer 9

1. salt formation (with NaOH)
   2.Ester formation (with alkaline/ Acetyl chloride)
   3.reduction with zn (forms benzene +ZnO)

Question 10

addition reactions of phenol

Answer 10

1. Nitration (dil. HNO3) forms ortho and para nitrophenol
   (conc HNO3) forms Picirc acid.(2,4,6 trinitrophenol)

2.hydrogenation (removes inner ring)

3. halogenation (electrophillic sub)
   produces 2,4,6 tribromophenol [White ppt]
4. Sulfonation[conc H2SO4]
   produces Hydroxybenzene sulfonic acid.

Question 11

base catalyzed reactions of Aldehydes/Ketones

Answer 11

1. HCN (all ald/ketone)
   produces cyanohydrins which, on hydrolysis of triple bond makes a-hydroxyacids.

2.sodium bisulphite NaHSO3 (only methyl ketones)
white ppt produced

3.Aldol condensation
aldol on heating with dil.acid produces Crotonaldehyde

4.Canizzaro’s reaction (self redox)
{aldehydes with no a-hydrogen react with alkali to form -OH and -COOH}

Question 12

acid catalysed (Aldehydes/ketones)

Answer 12

1.Ammonia derivatives
{addition elimination}

2.Hydroxylamine(NH2OH)
{form OXIMES}

3.Phenylhydrazine
{form phenyl hydrazones}

4.Hydrazine NH2NH2
{form hydrazones}

Question 13

identification of carbonyl compounds
1.only aldehydes
2.only ketones
3.both
4.only methyl ketones

Answer 13

1.tollens-silver mirror
Fehlings-red
benedit-brick red ppt of cuprous chloride

2.Sodium Nitroprusside-red

3. 2,4-DNPH
4. Sodium Bisulphite-White ppt

Question 14

trihaloalknes

Answer 14

alkanes with three halogen atoms

Question 15

alkyl halides are dihaloalkanes?

Answer 15

NO. monohaloalkanes.

Question 16

secondary alkyl halide

Answer 16

halogen atom attached to a carbon that is further attached to 2 carbon atoms

Question 17

B elimination reaction

Answer 17

removal of hydrogen and halogen from adjacent carbon atoms of alkyl halide.
b-hydrogen is necessary for elimination.

strong bases such as OH, NH2 cause elimination in preference to substitution

Question 18

E1 AND E2 REACTIONS

Answer 18

*same order of reactivity as SN1 AND SN2

E1 is two step reaction in which ionisation of alkyl halide and nucleophile attacks on b hydrogen in second step
[rate of reaction depends on conc of alkyl halide]
order; tertiary>secondary>primary

E2 single step.attack of nucleophile and removal of leaving group at the same time.
[rate dependant on alkyl halide and base]
order; primary>secondary>tertiary

Question 19

alkyl halides :substitution or elimination conditions

Answer 19

substitution is more favourable energetically
as elimination only occurs in presence of b hydrogen.

> primary alkyl halides favour substitution

> tertiary haloalkanes favour elimination because approach to a carbon is difficult for substitution

> strong bases favour elimination too. in presense of a strong base, main reaction is elimination and substitution is a side reaction.

> elimination is favoured more than by substitution by decreasing solvent polarity.
alcoholic KOH affects elimination while polar aq KOH used for substitution.

> increase in temperature favours elimination because less reorganization of bonds

Question 20

Test for identification bw alcohols

Answer 20

Lucas test (HCl in ZnCl2)
Immediate oily on 3⁰ alcohols
5 min 2⁰
On heat 1⁰

Question 21

Preparation of aldehydes and ketones

Answer 21

(Pg331ch12)

1.Formaldehyde
Lab method
passing a mixture of Methanol vapours over PT ASBESTOS AT 300⁰C
Industrial
passing a mixture of methanol vapours and air over silver catalyst 500⁰C

2. Acetaldehyde
   Lab method
   Oxidation of ethyl alcohol with H+/Na2Cr2O7
3. Acetone
   Prepared by dry distillation of calcium acetate.

Question 22

Aliphatic carboxylic acids

Answer 22

CarboxylicAcids attached with a H or an alkyl (R group)

Question 23

Aliphatic carboxylic acids

Answer 23

CarboxylicAcids attached with a H or an alkyl (R group)

Question 24

Preparation of carboxylic acids by?

Answer 24

1. Oxidation of 1⁰ alcohols
2. Hydrolysis if alkane nitriles C—N
3. Grignard reag(MgX) with CO²
4. Ester hydrolysis
5. Oxidation of alkenes

Question 25

Preparation of carboxylic acids by?

Answer 25

1. Oxidation of 1⁰ alcohols
2. Hydrolysis if alkane nitriles C—N
3. Grignard reag(MgX) with CO²
4. Ester hydrolysis
5. Oxidation of alkenes