Organic reagents

Question 1

What does Br2 in CCl4 react with and what are the observations?

Answer 1

Alkenes to form dibromoalkane: reddish-brown bromine decolourised
Phenols/phenylamines to form monobromo derivative: reddish-brown bromine decolourised
Alkanes/alkyl chains with heat or uv: reddish-brown bromine decolourised

Question 2

What is the rxn when Br2 in CCl4 react with alkenes/ phenols and phenylamines/ alkanes and alkyl chains?

Answer 2

alkenes: EA
phenols/phenylamines: ES
alkanes/alkyl chains: FRS

Question 3

What does Br2 with anhydrous FeBr3 or AlBr3 or Cl2 with anhydrous FeCl3 or AlCl3 react with? What is the reaction and observation?

Answer 3

benzene/substituted benzene to monobromo/chloro derivative formed
ES rxn
reddish-brown bromine decolourised

Question 4

What does Br2(aq) react with? What is the reaction and observation?

Answer 4

alkenes to bromoalcohol formed
EA rxn
orange/brown solution decolourised

Question 5

What does Br2(aq) react with other than alkenes? What is the reaction and observation?

Answer 5

phenols/phenylamines to tri-bromo derivative formed
ES rxn
orange/brown solution decolourised + white ppt formed

Question 6

What does AgNO3(aq) react with? What is the reaction and observation?

Answer 6

acid chlorides: hydrolysis
white ppt (AgCl)
acid bromides: hydrolysis
cream ppt (AgBr)

Question 7

What does H2O(l) react with? What is the reaction and observation?

Answer 7

acid halides to carboxylic acid and halogenoalkane: hydrolysis
white fumes
RCOX + H2O -> RCO2H + HX
(X= Cl/Br)

Question 8

What does Hbr(g) generated from NaBr with conc. H2SO4 and heat react with? What is the reaction and observation?

Answer 8

alcohols
bromine replaces -OH grp
substitution rxn
CH3CH2-OH + HBr -> CH3CH2-Br + H2O

Question 9

What does HCl(g) with anhydrous ZnCl2 catalyst react with? What is the reaction and observation?

Answer 9

alcohols
chlorine replaces -OH grp
substitution rxn
CH3CH2-OH + HCl -> CH3CH2-Cl + H2O

Question 10

What does 2,4-DNPH react with? What is the rxn and observation?

Answer 10

aldehydes/ketones to form hydrazone derivative
condensation rxn
orange ppt formed

Question 11

What does Fehling’s soution warm react with? What is the rxn and observation?

Answer 11

aldehydes (except benzaldehyde)
oxidation rxn : Cu2+ reduced to Cu+(Cu2O)
reddish-brown ppt formed

Question 12

What does Tollens’ reagent (Ammonical silver nitrate) warm react with? What is the rxn and observation?

Answer 12

aldehydes and benzaldehyde
oxidation rxn: Ag+ reduced to Ag(s)
silver mirror formed

Question 13

What does I2(aq) with NaOH(aq) warm react with? What is the rxn and observation?

Answer 13

alcohols with methyl group/ carbonyls with methyl group

yellow crystals of tri iodomethane(CHI3) formed

Question 14

What does HCN (with trace of NaOH or with trace of KCN) cold react with? What is the rxn and observation?

Answer 14

aldehydes and ketones
NA rxn : CH3COCH3 + HCN -> (CH3)2C(OH)CN
carbon chain extended by one 2 functional grps on one carbon atom

Question 15

What does dilute acids (HCL,H2SO4) heat react with? What is the rxn and observation?

Answer 15

nitriles/amides/esters
acid hydrolysis : 
CH3CN + H+ +2H2O -> CH3C02H + NH4+
CH3CONH2 + H+ + H2O -> CH3C02H + NH4+
CH3CO2CH3 + H2O -> CH3C02H + CH3OH

Question 16

What does conc. H2SO4 react with? What is the rxn and observation?

Answer 16

alkenes
EA rxn
CH2=CH2 + H2O -> CH3CH2OH

Question 17

What does excess conc. H2SO4 heat (170 degrees) react with? What is the rxn and observation?

Answer 17

alcohols: -OH and -H atom removed to form alkene

elimination rxn

Question 18

What does conc. H2SO4 heat react with? What is the rxn and observation?

Answer 18

alcohols + carboxylic acids
condensation rxn
conc. sulfuric acid is used as catalyst removing water from rxn pushing the eqm. to favour production of esters

Question 19

What does conc. HNO3 with H2SO4 (55/30 degrees) react with? What is the rxn and observation?

Answer 19

55 degrees: benzenes to nitrobenzene
ES rxn
pale yellow liquid

30 degrees: alkylbenzenes to nitromethylbenzene
ES rxn
pale yellow liquid

Question 20

What does conc. HNO3 react with? What is the rxn and observation?

Answer 20

phenols tri-substitution occurs
ES rxn
yellow solid
mono-sub when dilute nitric acid used

Question 21

What does neutral FeCl3(aq) react with? What is the rxn and observation?

Answer 21

phenols
complex formation
violet colouration

Question 22

What does KMnO4 with dil. H2SO4 heat react with? What is the rxn and observation?

Answer 22

look at notes

Question 23

What does dilute KMnO4 with NaOH(aq) cold react with? What is the rxn and observation?

Answer 23

alkenes to produce diols
mild oxidation
purple KMnO4 decolourised and black ppt of MnO2 formed

Question 24

What does dilute K2Cr2O7 with dil H2SO4 heat/heat with immediate distillation react with? What is the rxn and observation?

Answer 24

primary alcohol to carboxylic acid/secondary alcohol to ketone/aldehydes to carboxylic acid
oxidation
orange solution turns green

immediate distillation: primary alcohols to aldehydes
oxidation
orange solution turns green

Question 25

What does Na(s) react with? What is the rxn and observation?

Answer 25

Alcohols/phenols/carboxylic acids to give salt and hydrogen gas redox rxn effervescence

Question 26

What does NaOH(aq) room temp. react with? What is the rxn and observation?

Answer 26

phenols/carboxylic acids to give salt and water acid-base rxn phenols/carboxylic acids insoluble in water will dissolve in NaOH(aq)

Question 27

What does NaOH(aq) heat. react with? What is the rxn and observation?

Answer 27

halogenoalkanes: RX + OH- -> ROH + X- NS rxn distinguish diff HX with excess HNO3(aq) to resultant solution and add AgNO3 to ppt the silver halides AgCl: white ppt AgBr: cream ppt AgI: yellow ppt amides/nitriles to give ammonia gas and carboxylate salt secondary amides carboxylate salt and amine alkaline hydrolysis ammonia gas liberated turns moist red limus paper blue esters to give carboxylate salt and alcohol/phenoxide salt alkaline hydrolysis

Question 28

What does Na2CO3(aq) or NaHCO3(aq) react with? What is the rxn and observation?

Answer 28

carboxylic acids to give salt, water and carbon dioxide acid-base rxn effervescence

Question 29

What does NaOH dissolved in ethanol heat react with? What is the rxn and observation?

Answer 29

halogenoalkane to remove halogen atom and hydrogen atom on adjacent carbons elimination rxn

Question 30

What does NH3 react with? What is the rxn and observation?

Answer 30

carboxylix acid to give CH3CO2-NH4+ acid-base rxn acid chloride/bromide to give CH3CONH2+ HX acid-base rxn white fumes

Question 31

What does NH3 dissolved in ethanol heat in sealed tube react with? What is the rxn and observation?

Answer 31

halogenoalkane to give CH3NH2 + HX NS rxn excess halogenoalkane may cause further substitution

Question 32

What does PCl5/PCl3/SOCl2/PBr3 react with? What is the rxn and observation?

Answer 32

alcohols/carboxylic acids substitution rxn white fumes PCl5 also reacts with water to form white fumes rxn must be in anhydrous environment

Question 33

What does KCN or NaCN in ethanol heat react with? What is the rxn and observation?

Answer 33

halogenoalkanes to form CH3CH2CN + X- NS rxn carbon chain increased by one

Question 34

What does Sn with conc. HCl heat react with? What is the rxn and observation?

Answer 34

nitrobenzenes to form phenylamine reduction NaOH is added to liberate phenylamine (neutralize C6H5NH3+)

Question 35

What does NaBH4 react with? What is the rxn and observation?

Answer 35

aldehydes/ketones to give alcohol reduction CH3CHO + 2[H] -> CH3CH2OH (CH3)2CHO + 2[H] -> (CH3)2CHOH

Question 36

What does LiAlH4 in dry ether react with? What is the rxn and observation?

Answer 36

nitriles/aldehydes/ketones/carboxylic acids/esters/amides reduction LiAlH4 does not reduce alkenes

Question 37

What does H2(g) with Ni catalyst high temp and pressure react with? What is the rxn and observation?

Answer 37

alkenes/aldehydes/ketones/nitriles | reduction

Question 38

What is the confirmatory test for alkenes?

Answer 38

Br2(aq) | orange/brown solution decolourised

Question 39

What is the confirmatory test for phenol and phenylamine?

Answer 39

Br2(aq) | orange/brown solution decolourised white ppt formed

Question 40

What is the confirmatory test for aldehyde and ketones?

Answer 40

2,4-DNPH orange ppt formed hydrazone has well-defined melting point to identify aldehyde or ketone

Question 41

What is the confirmatory test for aldehyde except benazldehyde?

Answer 41

fehling's solution warm | reddish-brown ppt formed Cu2O

Question 42

What is the confirmatory test for compounds with phenol functional group?

Answer 42

``` neutral FeCl3(aq) violet colouration ```

Question 43

What is the confirmatory test for nitriles and amides?

Answer 43

NaOH(aq) heat | ammonia gas liberated turns moist red litmus paper blue

Question 44

What is the confirmatory test for carboxylic acids?

Answer 44

Na2CO3 or NaHCO3 | effervescence due to carbon dioxide produced

Question 45

What does HBr(g)/ HCl(g) react with? What is rxn and observation?

Answer 45

alkenes | EA