Appendix chemical test, routes of synthesis


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Appendix chemical test, routes of synthesis

  1. 1. Appendix APPENDIX 1 Chemical tests for functional groupsHomologous series/ Functional Chemical tests/Observations Typical compound group(s)Alkanes C – C and Add liquid bromine in ultraviolet light (or sunlight):CH3CH3 C–H White fumes of HBr liberated; decolourisation of bromineethane occurs slowlyAlkenes (a) Add Br2 in CCl4 at room temperature: C=CCH2 = CH2 Decolourisation of bromine occurs immediately ethene CH2 = CH2 + Br2 → CH2BrCH2Br (b) Add acidified KMnO4 at room temperature: Decolourisation of KMnO4 occurs immediately CH2 = CH2 + [O] + H2O → CH2 – CH2 ⏐ ⏐ OH OHAromatic (a) Insert a glowing splint into the hydrocarbonhydrocarbons hydrocarbons: Burns with smoky flame (b) Add concentrated nitric(v) acid and concentrated benzene sulphuric acid at 55 °C: Yellow oil with bitter almond smell produced NO2 H2SO4 + HNO3 (HONO2) + H2OAlkylbenzenes – CH3 Add alkaline KMnO4 and boil: CH3 Decolourisation of KMnO4; brown precipitate of MnO2 formed ⎯ CH3 + 3[O] ⎯ COOH + H2O methylbenzene Comment Oxidation of the side chain is more effective in alkaline than acidic conditions.Haloalkanes C–X Add silver nitrate in alcohol and warm:R–X White precipitate for C – Cl group; cream-colouredwhere R is an alkyl precipitate for C – Br group; yellow precipitate for C – Igroup; X is Cl, Br or I groupAlcohols – OH (a) Add solid PCl5:CH3CH2OH White fumes of HCl liberated ethanol C2H5OH + PCl5 → C2H5Cl + POCl3 + HCl(g) (b) Add glacial ethanoic acid and a few drops of concentrated sulphuric acid and heat: Fragrant fruity smell of ester liberated CH3COOH + C2H5OH → CH3COOC2H5 + H2O Appendix 1
  2. 2. Homologous series/ Functional Chemical tests/Observations Typical compound group(s)Aldehydes H (a) Add 2,4-dinitrophenylhydrazine at room temperature:CH3CHO ⏐ Yellow-orange precipitate formedethanal –C=O NO2 CH3CHO + H2NNH ⎯ ⎯ NO2 NO2 CH3CH = NNH ⎯ ⎯ NO2 + H2O (b) Add ammoniacal silver nitrate (Tollens’ reagent) and warm: CH3CHO + 2Ag+ + H2O → CH3COOH + 2Ag + 2H+ (c) Add Fehling’s solution (alkaline copper(II) complex) and heat: CH3CHO + 2Cu2+ + 2H2O → CH3COOH + Cu2O + 4H+Ketones O (a) Add 2,4-dinitrophenylhydrazine at room temperature:CH3COCH3 Yellow-orange precipitate formedpropanone –C–C–C NO2 NO2 CH3 CH3 C = O + H2NNH ⎯ ⎯ NO2 C = NNH ⎯ ⎯ NO2 + H2O CH3 CH3 (b) Add Tollens’ reagent or Fehling’s solution and heat: No reactionCarboxylic acids O (a) Add Na2CO3 solution at room temperature:CH3COOH Effervescence and carbon dioxide gas liberatedethanoic acid – C – OH 2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O (b) Add ethanol and a few drops of concentrated sulphuric acid and heat: Fragrant, fruity smell of ester liberatedEthanoate ions O (a) Add dilute sulphuric acid, then warm:CH3COO– Vinegar smell liberated –C–O– CH3COO– + H+ → CH3COOH (b) Add iron(III) chloride solution: Dark red solution produced 3CH3COO– + Fe3+ → (CH3COO)3FeMethanoate ions O (a) Add ammoniacal silver nitrate solution, then warm:HCOO– Grey precipitate or silver mirror of metallic silver formed H–C–O– HCOOH + Ag2O → 2Ag + CO2 + H2O (b) Add concentrated sulphuric acid and heat: Carbon monoxide liberated which burns with a blue flame HCOO– + H+ → H2O + COBenzoate ions O (a) Dissolve the organic salt in water, then add dilute COO– hydrochloric or sulphuric acid to the aqueous solution C6H5 – C – O – obtained: White precipitate of benzoic acid formed ⎯ COO– + H+ ⎯ COOH2 Appendix
  3. 3. Homologous series/ Functional Chemical tests/Observations Typical compound group(s) (b) Add iron(III) chloride solution: Buff-coloured precipitate formed 3 ⎯ COO– + Fe3+ ( ⎯ COO)3FeAmides – CONH2 Add aqueous sodium hydroxide, then warm:CH3CONH2 Ammonia gas liberated; it forms white fumes with hydrogenethanamide chloride gas CH3CONH2 + NaOH(aq) → CH3COONa + NH3Aliphatic primary – NH2 Add sodium nitrite (NaNO2), followed by dilute hydrochloricamines acid, then warm:C2H5NH2 Effervescence occursethylamine NaNO2/HCl RNH2 + O = N – OH ⎯⎯⎯⎯⎯→ ROH + N2 + H2O (HNO2) nitrous acidAcyl chloride O (a) Add ethanol and shake:CH3COCl White fumes of HCl liberatedethanoyl chloride – C – Cl On pouring reaction mixture into a beaker of water, fragrant smell of ester produced CH3COCl + C2H5OH → CH3COOC2H5 + HCl (b) Add aqueous silver nitrate at room temperature: White precipitate of silver chloride formed CH3COCl + AgNO3 + H2O → CH3COOH + AgCl + HNO3Amino acids – CHCOOH Add copper(II) sulphate solution:H2NCH2COOH ⏐ Dark blue solution of copper(II) complex formedaminoethanoic acid NH2Phenols OH (a) Add bromine water at room temperature: OH Decolourisation of bromine water and white precipitate formed OH OH Br Br phenol + 3Br2 + 3HBr Br (b) Add iron(III) chloride solution at room temperature: Purple solution producedArylamines NH2 (a) Add bromine water at room temperature: NH2 Decolourisation of bromine water and white precipitate formed NH2 NH2 Br Br phenylamine + 3Br2 + 3HBr Br (b) Add sodium chlorate(I) solution: Purple solution produced Appendix 3
  4. 4. APPENDIX 2 Tests to distinguish between organic compounds(A) Aliphatic Organic Compounds To distinguish between Chemical tests Observations Alkene and alkane Add Br2 in CCl4 Alkene: Immediate decolourisation (or cycloalkane) Alkane (or cycloalkane): No reaction Alcohol and ether Add PCl5 Alcohol: White fumes of HCl Ether: No reaction CH3CH2OH and CH3OH Iodoform C2H5OH: Yellow precipitate of iodoform (triiodomethane) (CHI3) formed (positive test) test: Add I2 in CH3OH: No visible reaction NaOH(aq), then warm CH3CH2OH and CH3CH2CH2OH Iodoform test C2H5OH: Positive iodoform test CH3CH2CH2OH: No reaction CH3CHCH3 and CH3CH2CH2OH Iodoform test CH3CH(OH)CH3: Positive iodoform test ⏐ CH3CH2CH2OH: No reaction OH Aldehyde (RCHO) and (a) Silver mirror test: Aldehyde: Silver mirror formed ketone (RCOR) Add Tollens’ Ketone: No reaction reagent, then warm (b) Add Fehling’s Aldehyde: Reddish-brown precipitate of solution, then Cu2O formed heat Ketone: No reaction CH3COCH2CH2CH3 and Iodoform test CH3COCH2CH2CH3: Positive iodoform test CH3CH2COCH2CH3 CH3CH2COCH2CH3: No reaction HCOOH (or its salts) and Acidified KMnO4 HCOOH (or its salts): Decolourisation of CH3COOH (or its salts) and heat KMnO4 CH3COOH (or its salts): No reaction COOH (or its salts) and Acidified KMnO4 COOH (or its salts): Decolourisation of ⏐ and heat ⏐ KMnO4 COOH COOH CH3COOH (or its salts) CH3COOH (or its salts): No reaction COOH and HCOOH Add concentrated COOH: Gives CO(g) and CO2(g) ⏐ sulphuric acid, then ⏐ (limewater turns milky) COOH heat COOH HCOOH: Only CO(g) liberated which has no effect on limewater CH3COONH4 and CH3CONH2 Add FeCl3 solution CH3COONH4: Dark red colouration due to formation of (CH3COO)3Fe CH3CONH2: No visible reaction H2NCH2COOH and ClCH2COOH Add copper(II) H2NCH2COOH: Deep blue colouration sulphate solution formed ClCH2COOH: No reaction4 Appendix
  5. 5. To distinguish between Chemical tests Observations COOC2H5 and CH3COOC2H5 Reflux with COOC2H5: KMnO4 decolourised ⏐ NaOH(aq); distill ⏐ COOC2H5 off the ethanol COOC2H5 produced; acidify the CH3COOC2H5: No reaction residual solution; add KMnO4 solution CH3CH2Br and CH3CH2Cl Add silver nitrate in CH3CH2Br: Yellow precipitate formed ethanol and warm CH3CH2Cl: White precipitate formed(B) Aromatic Compounds To distinguish between Chemical tests Observations C6H5CH3 and benzene Add KMnO4 in C6H5CH3: KMnO4 decolourised and brown alkaline solution, precipitate formed then boil Benzene: No reaction CH3C6H4OH and C6H5CH2OH (a) Bromine water CH3C6H4OH: Decolourisation and white precipitate formed C6H5CH2OH: No reaction (b) PCl5 C6H5CH2OH: White fumes CH3C6H4OH: No reaction C6H5CHO and C6H5COCH3 Add Tollens’ reagent, C6H5CHO: Silver mirror formed then warm C6H5COCH3: No reaction Comment Fehling’s solution cannot be used, as C6H5CHO has no effect on Fehling’s solution C6H5CH2CHO and CH3C6H4CHO Add Fehling’s C6H5CH2CHO: Yellow-orange precipitate solution, then heat of Cu2O formed CH3C6H4CHO: No reaction C6H5CH2Cl and C6H5Cl Add AgNO3 in C6H5CH2Cl: White precipitate ethanol, then heat C6H5Cl: No reaction CH3C6H4COOH and CH3C6H4OH Add Na2CO3 solution CH3C6H4COOH: Effervescence, CO2 at room temperature liberated CH3C6H4OH: No reaction CH3C6H4NH2 (or C6H5NH2) and Add bromine water CH3C6H4NH2 (or C6H5NH2): Bromine C6H5CH2NH2 decolourised and white precipitate formed C6H5CH2NH2: No reaction(C) Aliphatic and Aromatic Compounds To distinguish between Chemical tests Observations Benzene and hexane Add nitrating Benzene: Yellow oil formed mixture Hexane: No visible reaction (concentrated HNO3 + concentrated H2SO4) at 55 °C Appendix 5
  6. 6. To distinguish between Chemical tests ObservationsCyclohexene and benzene (a) Br2 in CCl4 (or Cyclohexene: Bromine decolourised bromine water) Benzene: No reaction (b) Acidified Cyclohexene: KMnO4 decolourised KMnO4 at room Benzene: No reaction temperatureC6H5COOC2H5 and Reflux the esters C6H5COOC2H5: White precipitate ofCH3COOC2H5 with aqueous NaOH, C6H5COOH formed distill off the ethanol CH3COOC2H5: No precipitate formed produced, add excess sulphuric acid to the residual liquidC6H5CHO and CH3COCH3 (a) Add Tollens’ C6H5CHO: Silver mirror formed reagent, then CH3COCH3: No reaction warm (b) Iodoform C6H5CHO: No reaction (triiodomethane) CH3COCH3: Yellow precipitate of CHI3 test formed (positive test)CH3COOH and C6H5OH (a) Na2CO3 solution CH3COOH: Effervescence; CO2 liberated at room C6H5OH: No reaction temperature (b) Bromine CH3COOH: No reaction water at room C6H5OH: White precipitate of temperature 2,4,6-tribromophenol formedC6H5OH and C2H5OH (a) Bromine C6H5OH: White precipitate of 2,4,6- water at room tribromophenol formed temperature C2H5OH: No reaction (b) Iodoform test C6H5OH: No reaction C2H5OH: Positive iodoform testC6H5NH2 and C2H5NH2 Add bromine water C6H5NH2: White precipitate of at room temperature 2,4,6-tribromophenylamine formed C2H5NH2: No reactionC6H5CONH2 and C2H5NH2 Add NaOH(aq) and C6H5CONH2: Ammonia gas liberated heat C2H5NH2: No reactionC6H5CONH2 and C2H5CONH2 Add NaOH(aq), C6H5CONH2: Ammonia gas liberated; then boil; add excess on acidification, white sulphuric acid to the precipitate of C6H5COOH reaction mixture on formed cooling C2H5CONH2: Ammonia gas liberated; on acidification, no precipitate formed6 Appendix
  7. 7. K2Cr2O7/H+ K2Cr2O7/H+ PCl5 NH3 C2H4Br2 C2H6 (CH2)n C2H5OH CH3CHO CH3COOH CH3COCl CH3CONH2 APPENDIX O 4 OH 2 H SO LiAlH4 COOH 2 Na C Br 2 + H H2SO4 0 3 H2,Ni 0° 30 /H 20 atm 4 200 °C OCOCH3 C2H5HSO4 C2H5ONa SO O4 2 H 2S COOH H CH2 CH3COOH O O2/Ag 0 °C CH3COOH 18 HN CH2 C2H4 C2H5OH NaOH, reflux O 4, aspirin NaOH, reflux 250 °C HX O2 H 2S OH 5 C 4 H P/I2 C2H5OH 2 0° H2O C OH nO CH3COOC2H5 CH3CN CH3OH CH3I CH3COOC2H5 14 5 H NaOH 2 KM /C CH2OH KCN Na alc. reflux CH2OH NH3 Li C2H5OC2H5 C2H5X C2H5NH2 CH3Li ether H+ KCN alloy Na/Pb alcohol O K2Cr2O7/H+ (CH3)3Pb + H– heat N K2Cr2O7/H a/ Na/C2H5OH C2H5NH3+ Pb C2H5CH2NH2 C2H5CN C2H5MgX Mg HS Grignard 2O ether HNO2 4 reagent COOH refl COOH K2Cr2O7/H+ ux CH3CH2COOH HCHO C2H5CH2OH CH3CH2CHO COOH LiAlH4 H2SO4 Cr2O72–/H+ KMnO4/H+ (CH3CH2)4Pb 180 °C HCHO R R’ C O HOOC Br2 H2SO4 + HCOOH acid RCHO CO2 + H2O CH3CH=CH2 CH3CHBrCH2Br CO + H2O heat + H C2H5CH2OH acid R Terylene r 2 SO R’ C—OH HB H 4 MnO4–/H+ 2O C2H5 Routes for the synthesis of aliphatic compounds R NaOH K2Cr2O7 CHOH CH3CHBrCH3 CH3CH(OH)CH3 CH3COCH3 CO2 + H2O C2H5 reflux H2SO4Appendix7
  8. 8. 8Appendix OH APPENDIX CH3 CrO2Cl2 LiAlH4 HNO3 CHO —CH2OH HOOC(CH2)4COOH KM 4 KMn nO O4 /H + 4 /H + Cl O LiAlH4 K2Cr2O7/H+ NH2(CH2)6NH2 C—CH3 H2, Ni 15 O H, COOH 200 °C C 2H 5O Na nylon atm eat Cl C—OC2H5 HCl, h CH3Cl/AlCl3 OH CO , 30 3 COCl, NaOH O 20 ,N i 0 CH 0 °C H 2 °C OH heat C—O H O—OH 250 °C, 25 atm, H3PO4 O2, 120 °C H2SO4 C—CH3 C—CH3 + CH3COCH3 NaOH (aq) CH3CH=CH2 100 °C reflux CH3 CH3 e 25 ,F cumene 0 2 Cl /A C 2 °C H 4 , 40 l3 —N 2 + Cl a H H CO2Na + O–Na+ lC tm Fe2O3 polymerisation C2H5 CH=CH2 ( ) —C—C—n 600 °C N=N OH H 55 °C u.v. HNO3/H2SO4 2 Cl , NO2 OH NH2 N2+Cl– OH Br Br Sn/HCl HNO2 H2O Br2 5 °C 70 °C l H 2, N Cl HC 20 Br Cl Cl CH3COCl OH 0° i OH O C NH3+Cl– NHCOCH3 K2Cr2O7/H+ Cl Cl Routes for the synthesis of aromatic compounds Cl N=N OH heat
  9. 9. APPENDIX 5 Reactions of bromine with organic compounds Organic compound Observations Reaction type/EquationsAlkene, cycloalkene or Immediate decolourisation Electrophilic addition reactionalkyne CH2 = CH2 + Br2 → CH2BrCH2Br Br + Br2 Br H – C ≡ C – H + 2Br2 → CHBr2CHBr2Phenol or Decolourisation and white Electrophilic substitution reactionphenylamine precipitate formed OH Br Br – OH + 3Br2 + 3HBr Br NH2 Br Br – NH2 + 3Br2 + 3HBr BrAldehyde or ketone No reaction with bromine Substitution reaction alone; decolourisation CH3COCH3 + Br2 → BrCH2COCH3 +HBr occurs only in the presence of a dilute acidAlkanes or Decolourisation occurs Free radical substitution reactioncycloalkanes slowly in uv light or RH + Br2 → RBr + HBr sunlight; no reaction in the dark at room temperatureBenzene or No reaction with bromine Electrophilic substitution reactionalkylbenzene alone; decolourisation occurs only in the presence + Br2 ⎯ Br + HBr of a halogen carrier such as iron filings CH3 CH3 CH3 Br + 2Br2 + + 2HBr Br Appendix 9
  10. 10. Reactions of aqueous sodium hydroxide with organic APPENDIX 6 compounds Reaction type Organic compound(s) Equation(s)Alkaline hydrolysis Haloalkane (alkyl halide) RX + NaOH → ROH + NaX CH2XCH2X + 2NaOH → CH2OHCH2OH + 2NaX Ester RCOOR + NaOH → RCOONa + ROH Amide RCONH2 + NaOH → RCOONa + NH3 C6H5NHCOCH3 + NaOH → C6H5NH2 + CH3COONa Nitrile RCN + H2O + NaOH → RCOONa + NH3NaOH as a base Ammonium salt RCOONH4 + NaOH → RCOONa + NH3 + H2O Amine salt RNH3+Cl– + NaOH → RNH2 + NaCl + H2O APPENDIX 7 Reactions of sulphuric acid with organic compounds Role of sulphuric acid Organic compound(s) Reaction(s)/Equation(s)As a catalyst for acid Ester RCOOR + H2O RCOOH + ROHhydrolysisAs a strong acid Carboxylate Strong acid displaces weaker acid from its salt RCOONa + H – HSO4 → RCOOH + NaHSO4 Amine Amines react with acids to form salts RNH2 + H – HSO4 → RNH3+HSO4–As a dehydrating agent Methanoic acid and Concentrated H2SO4 removes water molecules ethanedioic acid from HCOOH and H2C2O4 (ethanedioic acid) or their salts on heating H2SO4 HCOOH ⎯⎯→ CO + H2O H2SO4 H2C2O4 ⎯⎯→ CO + CO2 + H2OAs an electrophile in Alkenes Concentrated H2SO4 reacts with alkenes to formelectrophilic addition addition productsreactions with alkenes RCH = CH2 + H – OSO3H → RCHCH3 (H2SO4) ⏐ OSO3H10 Appendix
  11. 11. APPENDIX 8 Reactions of iron(III) chloride with organic compounds Organic compound(s) Observation Salts of carboxylic acid, for example, methanoate Red solution formed; brown precipitate obtained (HCOO–) or ethanoate (CH3COO–) when boiled Benzoate COO– Buff-coloured precipitate formed benzoate ion Phenol, phenoxide ion and 2-hydroxybenzoic acid OH O– COOH OH Purple solution formed phenol phenoxide 2-hydroxybenzoic ion acid APPENDIX 9 Uses of potassium manganate(VII) in organic chemistry(a) To distinguish alkenes from alkanes or cycloalkanes Alkenes decolourise acidified KMnO4 at room temperature or on heating. Alkanes and cycloalkanes do not react with KMnO4.(b) To distinguish between alkenes • Alkenes with a terminal = CH2 group not only decolourise hot, acidified KMnO4, but also liberate carbon dioxide. This is because a terminal = CH2 group is completely oxidised to carbon dioxide and water by hot KMnO4. The remaining RCH = group is oxidised to RCOOH. • Alkenes without a terminal = CH2 group decolourise hot, acidified KMnO4 but do not liberate carbon dioxide.(c) To identify the position of the double bond in an alkene The oxidation products obtained when an alkene reacts with hot, acidified KMnO4 are often used to determine the position of the double bond of an unknown alkene.(d) To distinguish aldehydes from ketones Aldehydes are oxidised by acidified KMnO4 on heating to form carboxylic acids. Thus aldehydes decolourise acidified KMnO4 on heating. In contrast, ketones do not decolourise hot, acidified KMnO4.(e) To distinguish alkylbenzenes from benzene Alkylbenzenes such as ethylbenzene decolourise acidified or alkaline KMnO4 on heating. The alkyl group is oxidised to – COOH, for example, ⎯ CH2CH3 + 6[O] ⎯ COOH + CO2 + 2H2O ethylbenzene Benzene does not decolourise hot, acidified or alkaline KMnO4.(f) To distinguish primary or secondary alcohols from tertiary alcohols Primary and secondary alcohols can be oxidised to aldehydes and ketones respectively. Hence, primary and secondary alcohols decolourise hot, acidified KMnO4. Tertiary alcohols are resistant to oxidation and hence do not decolourise hot, acidified KMnO4. Appendix 11