Tiêu đề 02. Alkane FLow Carts.pdf ✅

TEACH HIRE DOWNLOAD APP FROM PLAY STORE CLICK HERE TEACH HIRE DOWNLOAD APP FROM PLAY STORE CLICK HERE ALKANE GENERAL INTRODUCTION • These are the hydrocarbons in which Carbon - Carbon contains single bond. (Saturated hydrocarbon). • These are also called as ‘Paraffins’ (Parum + Affinis i.e. less reactive). • In alkane if chiral carbon or unsymmetrical carbon is present, then it shows optical isomerism. • General reagents such as dil. and conc. HCl, dil. and conc.H2 SO4 , dil. and conc. HNO3 , acidic and basic KMnO4 and K2Cr2O7 usually does not react with alkane. • General formula is CnH2n+2 .(n = 1, 2, 3, 4..............) • Hybridisation state of carbon is sp 3 . • Geometry of carbon is tetrahedral. • Bond angle is 109o28’. • Number of bond angle in methane are six, while in ethane are twelve. H 2 1 H H H 4 5 6 3 Methane 2 1 H 4 5 5 6 6 4 H H H H H 1 2 3 3 Ethane • C–C bond length is 1.54 Å while C–H bond length is 1.12 Å. • C–C bond energy is 84 kcal/ mole while C–H bond energy is 98 kcal /mole. • Alkane shows only chain, position isomerism. • First three members methane, ethane and propane does not exhibit any isomerism, while butane and pentane shows only chain isomerism. H | C | H H– –H CH3 –CH3 CH3 –CH2 –CH3 CH3 –CH2 –CH2 –CH3 CH3 –CH | CH3 –CH3 Methane Ethane Propane n-Butane Isobutane CH3 –CH2 –CH2 –CH2 –CH3 CH3 –CH | CH3 –CH2 –CH3 CH3 | CH3–C–CH3 | CH3 CH3–CH2–CH2–CH2–CH2–CH3 n-Pentane IsoPentane NeoPentane n-Hexane CH3–CH2–CH–CH2–CH3 CH3 CH3–C–CH2–CH3 CH3 CH3 CH3–CH–CH2–CH2–CH3 CH3 CH3–CH–CH–CH3 CH3 CH3
3-Methyl pentane Neohexane Isohexane 2, 3-Dimethyl butane • The molecules of alkanes are angular , so carbon chains in these molecules are zig- zag type (not straight) which may be branched or unbranched as shown below. (Unbranched) (branched) PHYSICAL PROPERTIES • Alkanes are colourless, odourless and tasteless. • Physical state: C1 –→ C4 Gaseous state C5 –→ C17 Liquid state (except neo pentane) C18 & above –→ Solid like wax • Alkanes are lighter than water, so it floats over water. • Solubility : [Like dissolves like] Alkanes are non-polar or weakly polar compounds so these are soluble in non-polar solvents (benzene, ether, chloroform, carbontetrachloride etc.) and are insoluble in polar solvents (water etc.). • Boiling point : For homologues B.P.  Molecular weight because Mol. wt.  = Surface area  = Intermolecular Vander wall's interaction  = B.P.  For isomers B.P.  No.of branches 1 because Branches  = Spherical shape  = Surface area  = B.P.  • Melting point : The melting point of alkanes depends upon molecular weight as well as packing in crystal lattice
TEACH HIRE DOWNLOAD APP FROM PLAY STORE CLICK HERE TEACH HIRE DOWNLOAD APP FROM PLAY STORE CLICK HERE Variation of boiling point and melting point in alkanes Name Formula Molecular mass B.P. (oC) M.P. (oC) Methane CH4 16 –162 –183 Ethane CH3CH3 30 –88.5 –172 Propane CH3CH2CH3 44 –42 –187 n-Butane CH3 (CH2 )2CH3 58 0 –138 Isobutane (CH3 )2CHCH3 58 –12 –159 n-Pentane CH3 (CH2 )3CH3 72 36 –130 Isopentane (CH3 )2CHCH2CH3 72 28 –160 Neopentane (CH3 )4C 72 9.5 –17 n-Hexane CH3 (CH2 )4CH3 86 69 –95 n-Heptane CH3 (CH2 )5CH3 100 98 –90.5 n-Octane CH3 (CH2 )6CH3 114 126 –57 • Graphical representation : B.P. No. of carbon atoms [regular graph] [Irregular or zig-zag graph] No. of carbon atoms M.P.  M.P. (odd to even) >  M.P. (even to odd) Ques. Boiling point order ? (i) CH4 < CH3CH3 < CH3CH2CH3 (ii) CH3–C–CH3 CH3 CH3 < CH3–CH–CH2–CH3 CH3 < CH3CH2CH2CH2CH3 Ques. Melting point order ? (i) CH3CH2CH3 < CH4 < CH3CH3 (ii) CH3–CH–CH2–CH3 CH3 < CH3CH2CH2CH2CH3 < CH3–C–CH3 CH3 CH3  Maximum packing due to symmetrical spherical shape
CHEMICAL PROPERTIES OF ALKANE R–N O O Halogenation R–X X2/h or UV light Nitration HNO3/400oC Sulphonation H2S2O7 R–SO3H Reed reaction SO2 + Cl2/h R–SO2Cl AlCl3/HCl Isomerisation Branched alkane 500o–700oC Pyrolysis or Cracking Alkenes + CH4 or C2H6 500oC Cr2O3 + Al2O3 Aromatic compound step up reaction CH2N2/ Higher alkane O2 combustion CO2 + H2O + H C (exothermic) R–H or R–R (F2 > Cl2> Br2 > I2) Catalytic Oxidation O2 / Cu Mo2O3 (AcO)2 Mn R–CH2OH R–CHO R–COOH SO2Cl2/h R–Cl