Introduction to organic chemistry

21 21.1 21.2 21.3 21.4 1 Introduction to Organic Chemistry What is Organic Chemistry? The Unique Nature of Carbon Classification of Organic Compounds Factors Affecting the Physical Properties of Organic Compounds New Way Chemistry for Hong Kong A-Level Book 3A 21 What is Organic Chemistry? 2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.1 What is Organic Chemistry (SB p.2) Organic Chemistry 3 • Chemistry of the compounds present in living organisms • They all contain carbon • Organic Chemistry is the Chemistry of Carbon New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.1 What is Organic Chemistry (SB p.4) Natural Sources of Organic Compounds Living things Carbohydrates / Proteins / Fats / Vitamins / Antibiotics A variety of organic products obtained from living things 4 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.1 What is Organic Chemistry (SB p.4) Natural Sources of Organic Compounds Crude oil or coal Fractional distillation / destructive distillation Alkanes / Alkenes / Alkynes / Aromatic hydrocarbons Check Point 21-1 5 A variety of useful products derived from crude oil and coal New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.1 What is Organic Chemistry (SB p.3) Development of Organic Chemistry as a Science In the past …, Chemistry Chemistry Organic Organic compounds compounds obtained from living organisms 6 Inorganic Inorganic compounds compounds obtained from non-living sources New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.1 What is Organic Chemistry (SB p.3) Development of Organic Chemistry as a Science In 1828, Wohler (a German chemist) (Inorganic compound) 7 (Organic compound) New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.1 What is Organic Chemistry (SB p.3) Development of Organic Chemistry as a Science Redefining … Organic chemistry chemistry is is the the study study of of carbon carbon Organic compounds (except (except CO, CO, CO CO22,, carbonates, carbonates, compounds hydrogencarbonates, carbides carbides and and hydrogencarbonates, cyanides) obtained obtained from from natural natural sources sources or or cyanides) synthesized in in the the laboratories laboratories synthesized 8 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21 The Unique Nature of Carbon 9 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to form four strong covalent bonds • Electronic configuration of carbon (ground state) : 1s22s22p2 Carbon (ground state) 10 10 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.18) Why is oil immiscible with water? Oil molecules not have free OH groups, so they cannot form hydrogen bonds with water molecules Back 77 77 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A Answer 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20) The relative molecular mass of glucose is 180.0, but it is soluble in water Why? Answer Glucose molecules have OH groups, so they are able to form hydrogen bonds with water molecules Therefore, glucose is soluble in water despite it has a high molecular mass 78 78 Back New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20) Despite the fact that butan-1-ol and ethoxyethane have the same relative molecular mass, they have very different boiling points The boiling points of butan-1-ol and ethoxyethane are 117oC and 35oC respectively Explain the difference Answer 79 79 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.20) Back There is an OH group in butan-1-ol Thus, butan-1-ol molecules are able to form hydrogen bonds with one another and the energy required to separate butan-1-ol molecules would be much greater Whereas for ethoxyethane, the attraction among the molecules is weak van der Waals’ forces only The amount of energy required to break the forces would not be great Therefore, the boiling point of ethoxyethane is lower than that of butan-1-ol 80 80 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21) Back Explain why propan-1-ol is soluble in water but 1-chloropropane is insoluble in water Answer The  OH group of propan-1-ol molecules enables it to form hydrogen bonds with water molecules Thus it is soluble in water Although 1-chloropropane is a polar molecule, it does not form hydrogen bonds with water molecules So it is insoluble in water 81 81 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.21) Which molecule would have a higher boiling point, 1-bromobutane or 2-bromobutane? Why? Answer 1-bromobutane would have a higher boiling point 1-bromobutane is a straight-chain molecule while 2-bromobutane is a branched-chain molecule Straight-chain molecules have a greater surface area in contact with each other, so greater intermolecular forces exist among the molecules Higher energy is required to break down the intermolecular forces among the molecules of 1-bromobutane Back 82 82 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.22) 1-Chlorobutane and 2-chloro-2-methylpropane have the same molecular mass, yet their melting points differ The melting point of 1chlorobutane is –123oC while that of 2-chloro2-methylpropane is –27.1oC Explain the difference Answer 83 83 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.22) Back Melting point is a measure of how efficient the molecules are packed together in the solid state instead of just comparing the van der Waals’ forces among molecules Hence melting point is a function of the efficient packing of molecules but not the contact surface area 1-Chlorobutane is a straight-chain molecule while 2-chloro-2-methylpropane is a branched-chain molecule As 2-chloro-2-methylpropane is more spherical and symmetrical, its molecules are packed more efficiently in the solid state 1-Chlorobutane is linear in shape and flattened, its packing in the solid state is not so efficient Hence, it has a lower melting point than 2-chloro-2-methylpropane 84 84 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) (a) What are the major factors that affect the physical properties of organic compounds? Answer (a) 85 85 The physical properties of organic compounds are mainly affected by the structure of the functional groups, dipole moment of the molecule, the formation of hydrogen bonding between molecules, and the length of carbon chains of the molecule New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) (b) The melting point and boiling point of pentane are –130oC and 36.3oC respectively while the melting point and boiling point of 2,2dimethylpropane are –15.9oC and 9.5oC respectively Account for the difference in melting point and boiling point between the two isomers Answer 86 86 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) (b) 87 87 Pentane is a straight-chain molecule, while 2,2-dimethylpropane is a branched-chain molecule Straight-chain molecules have a greater surface area in contact with each other than branchedchain molecules Straight-chain molecules are held together by stronger intermolecular forces Therefore, pentane has a higher boiling point than 2,2-dimethylpropane Molecules of 2,2dimethylpropane are more spherical in shape and are packed more efficiently in the solid state Molecules of pentane are linear in shape and flattened, so their packing in the solid state is not efficient Since extra energy is required to break down the efficient packing of 2,2-dimethylpropane, 2,2-dimethylpropane has a higher melting point than pentane New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) (c) Which molecule, hexane or cyclohexane, would have a higher melting point? Explain your answer 88 88 Answer New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) (c) 89 89 Cyclohexane has a higher melting point than hexane Molecules of cyclohexane are more spherical in shape and are packed more eff iciently in the solid state Molecules of hexane are linear in shape and flattened, so their packing in the solid state is not efficient Since extra energy is required to break down the efficient packing of cyclohexane, cyclohexane has a higher melting point than hexane New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) (d) Arrange the following molecules in increasing order of boiling points Explain your answer 90 90 Answer New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.4 Factors Affecting the Physical Properties of Organic Compounds (SB p.24) Back (d) 91 91 The boiling points increase in the order: butane < propanal < propan-1-ol Molecules of butane are non-polar Their molecules are held together by weak instantaneous dipole-induced dipole interactions A relatively small amount of energy is required to separate the molecules in the process of boiling Both propanal and propan-1-ol are polar molecules Molecules of propanal are held together by relatively weak dipole-dipole interactions, while molecules of propan-1-ol are held together by intermolecular hydrogen bonds Since the intermolecular forces present in molecules of propan-1-ol are stronger than those present in molecules of propanal, a larger amount of energy is required to separate the propan-1-ol molecules in the process of boiling New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A [...]... of Carbon (SB p.5) Ability to form four strong covalent bonds • Each carbon atom has four unpaired electrons when excited • Tend to form four strong covalent bonds Carbon (excited state) 11 11 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate • Carbon atoms link together to form chains of varying length,... Groups • 20 20 Organic compounds are classified by the the presence of characteristic functional groups New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups A functional functional group group is is defined defined as as an an A atom or or aa group group of of atoms atoms that that atom effectively... effectively properties of of an an organic organic compound compound properties 21 21 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups 22 22 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds (SB p.7) Functional... Classification of Organic Compounds (SB p.13) 34 34 Example 21-3A Example 21-3B Example 21-3C Check Point 21-3 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 35 35 21 4 Factors Affecting the Physical Properties of Refer to notes on ‘Bonding and Structure’ Organic pp.77-92 – intermolecular forces Compounds New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry. .. Catenation:  Ability of atoms in forming stable bonds with itself, hence joining up into chains or rings 12 12 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate C – C > Si – Si > Ge – Ge > Sn – Sn Bond strength ↓ as bond length ↑ 13 13 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong... Ability to Catenate C–C>N–N>O–O Bond strength ↓ as the number of lone pairs ↑ 14 14 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.2 The Unique Nature of Carbon (SB p.5) Ability to Catenate 15 15 CnH2n+2 n = 1,2,3,…(no limit for n) SinH2n+2 n = 1 to 6 only → silanes GenH2n+2 n = 1 to 3 only → germanes SnnH2n+2 Only SnH4 (stannane) exists New Way Chemistry. .. sodium to give hydrogen gas New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds (SB p.7) Functional Groups and • have similar chemical properties  they contain the same functional group –OH  they are classified into the same homologous series — alcohols 24 24 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry. .. Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds (SB p.13) Homologous Series Functional group of an organic compound Chemical properties Members of a homologous series have similar chemical properties 30 30 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic. .. A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.2 The Unique Nature of Carbon (SB p.6) Example 21-2 18 18 Check Point 21-2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21 3Classification of Organic Compounds 19 19 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds... C4H10 CH2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 21.3 Classification of Organic Compounds (SB p.12) Number of carbon atom(s) IUPAC name Molecular formula Condensed structural formula 1 Methane CH4 CH4 2 Ethane C2H6 CH3CH3 3 Propane C3H8 CH3CH2CH3 4 Butane C4H10 CH3CH2CH2CH3 26 26 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong