按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A 1 1 Halogenoalkane compounds and Nucleophilic Substitution 30.1Introduction 30.2Nomenclature of Halogeno-compounds 30.3Physical Properties of Halogeno-compounds 30.4Preparation of Halogeno-compounds 30.5Nucleophilic Subsititution Reaction 30.6Elimination Reactions

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Introduction

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Introduction (SB p.208) Haloalkanes Organic compounds having one or more halogen atoms replacing hydrogen atoms in alkanes If there is one halogen atom replacing a hydrogen atom  General formula of haloalkanes: C n H 2n+1 X

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Introduction (SB p.208) Haloalkanes According to the number of alkyl groups attached to the carbon atom which is bonded to the halogen atom  haloalkanes are classified into primary, secondary or tertiary

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno- compounds

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno-compounds (SB p.209) Nomenclature of Halogeno- compounds The IUPAC rules for naming halogeno- compounds are similar to those for naming alkanes

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno-compounds (SB p.209) Nomenclature of Halogeno- compounds 1.The halogens are written as prefixes: fluoro- (F), chloro- (Cl), bromo- (Br) and iodo- (I) Numbers are assigned to the halogen substituent in the same way as the alkyl substituent

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno-compounds (SB p.209) Nomenclature of Halogeno- compounds e.g.

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno-compounds (SB p.209) Nomenclature of Halogeno-compounds 2.When the parent chain has both a halogen and an alkyl substituent  the chain is numbered from the end closest to the first substituent

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno-compounds (SB p.209) Nomenclature of Halogeno-compounds 2.When the parent chain has both a halogen and an alkyl substituent  the chain is numbered from the end closest to the first substituent  all the prefixes are listed in alphabetical order

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nomenclature of Halogeno-compounds (SB p.209) Nomenclature of Halogeno-compounds e.g.

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno- compounds

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.211) Physical properties of some halogeno-compounds NameMolecular formula Boiling point ( o C) Melting point ( o C) Density at 20 o C (g cm -3 ) Chloro- derivatives: ChloromethaneCH 3 Cl ChloroethaneCH 3 CH 2 Cl Chloropropane CH 3 (CH 2 ) 2 Cl ChlorobutaneCH 3 (CH 2 ) 3 Cl Chloropentane CH 3 (CH 2 ) 4 Cl ChlorohexaneCH 3 (CH 2 ) 5 Cl

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.211) Physical properties of some halogeno-compounds NameMolecular formula Boiling point ( o C) Melting point ( o C) Density at 20 o C (g cm -3 ) Bromo- derivatives: BromomethaneCH 3 Br BromoethaneCH 3 CH 2 Br Bromopropane CH 3 (CH 2 ) 2 Br BromobutaneCH 3 (CH 2 ) 3 Br Bromopentane CH 3 (CH 2 ) 4 Br BromohexaneCH 3 (CH 2 ) 5 Br

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.211) Physical properties of some halogeno-compounds NameMolecular formula Boiling point ( o C) Melting point ( o C) Density at 20 o C (g cm -3 ) Iodo- derivatives: IodomethaneCH 3 I IodoethaneCH 3 CH 2 I IodopropaneCH 3 (CH 2 ) 2 I IodobutaneCH 3 (CH 2 ) 3 I IodopentaneCH 3 (CH 2 ) 4 I IodohexaneCH 3 (CH 2 ) 5 I (Iodomethyl)- benzene C 6 H 5 CH 2 Idec

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.212) Boiling Point and Melting Point C  X bond is polar in nature  Difference in electronegativity between carbon and halogens Molecules of haloalkanes are held together by dipole-dipole interactions Haloalkanes have higher b.p. and m.p. than alkanes of comparable relative molecular masses

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.212) Boiling Point and Melting Point B.p. and m.p. of fluoro-, chloro-, bromo- and iodo- compounds increase in the order: RCH 2 F < RCH 2 Cl < RCH 2 Br < RCH 2 I Larger, more polarizable halogen atoms lead to  increase in dipole-dipole interactions between molecules

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.212) Boiling Point and Melting Point When the number of carbon atoms in the alkyl groups increases  the molecular size also increases  stronger dipole-dipole interactions between molecules  higher b.p. and m.p.

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.212) Variation of boiling points with the number of carbon atoms of straight-chain haloalkanes

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.212) Density When the relative molecular mass of haloalkanes increases  the densities of haloalkanes decrease Closer packing of the smaller molecules in the liquid phase Bromoalkanes and iodoalkanes are denser than water at 20 o C

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Physical Properties of Halogeno-compounds (SB p.213) Solubility Haloalkanes are immiscible with water But dissolve in organic solvents

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno- compounds

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno-compounds (SB p.218) Reactions of Halogeno-compounds C  X bond is polar  halogens are more electronegative than carbon The carbon atom bears a partial negative charge The halogen atom bears a partial positive charge

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno-compounds (SB p.218) Reactions of Halogeno-compounds One of the characteristic reactions of haloalkanes is nucleophilic substitution reactions:

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno-compounds (SB p.218) Reactions of Halogeno-compounds In the reaction,  the nucleophile attacks the electropositive carbon centre  displaces a halide ion from the haloalkane  a kind of substitution reactions

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno-compounds (SB p.218) Reactions of Halogeno-compounds  The reaction is initiated by a nucleophile  called nucleophilic substitution reaction

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno-compounds (SB p.219) Reactions of Halogeno-compounds Another characteristic reaction of haloalkanes is elimination reactions:

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Reactions of Halogeno-compounds (SB p.219) Reactions of Halogeno-compounds A base removes a hydrogen atom from the carbon atom adjacent to the C  X bond C=C bond is formed

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.219) Reaction with Sodium Hydroxide Consider the following reactions:

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.219) Reaction with Sodium Hydroxide In both reactions,  the nucleophile (OH - ) attacks the haloalkane  replacing the halogen atom with a hydroxyl group

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.221) 2. Stereochemistry of S N 2 Reactions The nucleophile attacks the electropositive carbon centre from the backside  the configuration of the carbon atom under attack inverts

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A 33 The Concentration and Strength of the Nucleophile 30.6 Nucleophilic Substitution Reactions (SB p.226) A negatively charged nucleophile (e.g. OH - ) is always a stronger nucleophile than a neutral nucleophile (e.g. H 2 O)

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A 34 The Concentration and Strength of the Nucleophile 30.6 Nucleophilic Substitution Reactions (SB p.227) In a group of nucleophiles in which the nucleophilic atom is the same, the order of nucleophilicity roughly follows the order of basicity e.g.oxygen compounds show the following order of reactivity: RO - > OH - >>ROH > H 2 O

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A 35 The Nature of the Leaving Group 30.6 Nucleophilic Substitution Reactions (SB p.227) BondBond enthalpy (kJ mol -1 ) C  F +484 C  Cl +338 C  Br +276 C  I +238 Bond enthalpies of carbon-halogen bonds

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.228) 6. Comparison of Rates of Hydrolysis of Haloalkanes Experiment 1: Comparison of the Rates of Hydrolysis of 1-Chlorobutane, 1-Bromobutane and 1-Iodobutane Three test tubes containing ethanol, silver nitrate solution and different haloalkanes

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.228) Results and Observation: AgCl(s) Test tube A AgBr(s) Test tube B AgI(s) Test tube C

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.229) Discussion: The ease of leaving of halide ions decreases in the order: I - > Br - > Cl - The order of precipitates appeared follows the order of ease of leaving of the halide ions Ag + (aq) + X - (aq)  AgX(s)

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.233) Reaction with Potassium Cyanide When a haloalkane is heated under reflux with an alcoholic solution of KCN or KCN in ethanol  a nitrile is formed

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.233) Reaction with Potassium Cyanide e.g.

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.233) Reaction with Potassium Cyanide CN - acts as a nucleophile Halobenzenes do not react with KCN

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.233) Reaction with Potassium Cyanide Nitriles can be hydrolyzed to carboxylic acids which can be reduced to alcohols Provides a useful way of introducing a carbon atom into an organic molecule  length of carbon chain can be increased

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.234) Reaction with Ammonia Ammonia is a nucleophile  Presence of a lone pair of electrons on the nitrogen atom

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.234) Reaction with Ammonia When a haloalkane is heated with an aqueous alcoholic solution of ammonia under high pressure  an amine is formed

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.234) Reaction with Ammonia e.g.

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.234) Reaction with Ammonia  Ethylamine will compete with ammonia as the nucleophile  a series of further substitution reactions takes place  a mixture of products is formed

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.234) Reaction with Ammonia The reaction stops at the formation of a quaternary ammonium salt

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Nucleophilic Substitution Reactions (SB p.234) Reaction with Ammonia The competing reactions can be minimized by using excess ammonia Not a satisfactory method for preparing amines  a mixture of amines is always formed

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.236) Formation of Alkenes Heating a haloalkane with a strong base (e.g. sodium hydroxide in ethanol)  causes the elimination of HX from adjacent carbon atoms of a haloalkane

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.236) Formation of Alkenes e.g.

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.236) Formation of Alkenes The reaction is also called as dehydrohalogenation

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.236) Formation of Alkenes Dehydrohalogenation of most haloalkanes yields more than one product

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.236) Formation of Alkenes The major product will be the more stable alkene  The more stable alkene has the more highly substituted double bond

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.237) Formation of Alkenes The order of stabilities of alkenes is:

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A Elimination Reactions (SB p.237) Formation of Alkenes Whenever an elimination reaction occurs to give the more highly substituted alkene as the major product  the elimination reaction follows the Saytzeff’s rule

按一下以編輯母片標題樣式 New Way Chemistry for Hong Kong A-Level Book 3A New Way Chemistry for Hong Kong A-Level 3A 57 The END