Assignment on Alkanes PDF
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Added on 2021-06-17
Assignment on Alkanes PDF
Added on 2021-06-17
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AlkanesCharacteristics of alkanes Alkanes being a critical fuel its filtration are done from the crude material of unrefinedpetroleum. Alkenes are created when long chain alkanes are 'broke' - and in light of the factthat they are reactive, they are often used as the starting point for chemical reactions, such asmaking plastics.(Kissim, 2001)The chemical behaviours of organic compounds are determined by functional groups whichare either an atom or group of atoms. It should be noted that organic compounds that willhave similar function group will have similarity on their chemical properties, example beingthat compounds that do contain a function group of -OOH (carboxylic) will undergo similarchemical reactions.Always the functional group takes the suffix name, while the other functional groups areconsidered as substituents and are use as the prefix name.
Process of substitution reactionA simple demonstration of substitution reaction of the alkane is when ethane is reacted withchlorine gas in the presence of light (UV light), the product will be 1-chloro methane andhydrogen chloride gas will be formed.CH3CH3+ Cl2→CH3CH2Cl + HClAlways an atom of the hydrogen atoms in the ethane will be replaced by a chlorine atomthrough substitution. Single unpaired electrons are contained on the free radicals are atoms orgroups of atoms. (Crute, T.D, 2000).Substitution reactions of methane with halogensExample of halogen include, chlorine, bromine and frorineThe stages of substitution process to effectively take place involve;1.Initiating the sunlight or UV light to break the chlorine molecules into their free radical atoms, that is;Chain initiationThe chain is initiated (started) by UV light breaking a chlorine moleculeinto free radicals.Cl22ClChain propagation reactionsThese are the reactions which keep the chain going.CH4+ ClCH3+ HClCH3+ Cl2CH3Cl + ClChain termination reactionsThese are reactions which remove free radicals from the system without replacing them by new ones.2ClCl2CH3+ ClCH3ClCH3+ CH3CH3CH3
2.Combination of the free radical atoms with alkyl group formed during carbon – hydrogen breaking down from their respective alkane groups.CH4+ ClCH3+ HClFurther propagation 3.The free radical formed at the end is eliminated from the product formed with their presence due to excess use of the halogens to facilitate complete substitution reactions. Dichloromethane Cl- + CH3Cl CH2Cl- + HClCl2 + CH2Cl- CH2Cl2 + Cl-Trichloromethane Cl- + CH2Cl2CH2Cl- + HClCl2 + CHCl2- CHCl3 + Cl-Tetrachloromethane Cl- + CHCl3CCl3- + HClCl2 + CCl3- CCl4 + Cl-(Crute, T.D, 2000)Why alkanes undergo substitution reactions.Sigma And Pi BondsA sigma bond is a covalent bond which is formed by the head on overlap of two atomic orbitals. The combination of overlapping orbitals can be s-s, s-pzor pz-pz. Sigma bonding can be a bonding interaction or an anti-bonding interaction. Bonding interaction results by the
overlapping of two atomic orbitals in the same phase whereas anti-bonding interaction occursby the overlapping in opposite phase.A Pi bond is a covalent bond which is formed by the side-to-side overlap of two atomic orbitals. The atomic orbital combinations can be px-pxor py-py.Similar to the sigma bonding, a pi bond can be bonding or anti-bonding.Sigma bonds are relatively stronger when compared with pi bonds. Hence, pi bonds are easilybroken while sigma bonds aren't. There can be only one sigma bond between two particular atoms in a molecule. But there can be a maximum of two pi bonds between two atoms in a molecule. For example,• If there is a single bond between two atoms, then the bond will be sigma bond.• If there are two bonds, then one will be sigma and another will be pi bond.• If there are three bonds, then one will be sigma bond and two will be pi bonds.Presence of pi bonds keeps the corresponding atoms in a plane. Increasing number of pi bonds will increase the electronegativity and % of ‘p’ character of the bond.Asp2hybridized orbital can have a one sigma and one pi bond and asphybridized orbital. The “sp-sphybridized orbital” can have one sigma and two pi bonds.Types of BondNumber of Sigma BondsNumber of Pi BondsAlkane (C-C)10Alkene ()11Alkyne ()12
Write up Oxidation of alcohol Alcohol are organic substance that contain hydroxyl group of –OH as their functional group, they can be oxidized by using acidified potassium dichromate in warm condition, to give a product that do vary in accordance with the type of alcohol used, the following are type of products formed with different type of alcohol used when oxidized.2.2 Give the name and structural formula of the product of oxidation of a given alcohol.From the image above it is observed that oxidation of alcohol results into different type of compounds depending on different conditions they are prepared from alcohol, but the functional group will still remain to be¿]Laboratory experiment: oxidation of ethanol Aim
To oxidize ethanolby using acidified sodium dichromate through first forming aldehyde then further oxidation toethanoic acid2.2 Describe the reagents and conditions used in oxidation of alcohols.Apparatus Chemicals Goggles to be wornBoiling tube (Note 1)Dropping pipetteTest-tube rackTest-tube holderBunsen burnerHeat resistant matEthanol (IDA, Industrial Denatured Alcohol) (HIGHLY FLAMMABLE, HARMFUL), 2 - 3 cm3, provided in small bottlesAcidified sodium dichromate(VI) solution, 10 cm3(VERY TOXIC, CORROSIVE)2.0 g of sodium bicarbonateProcedureaPlace about3 cm3of acidified sodium dichromate solution in a boiling tube.bUse a teat pipette to add 5 -7 drops of ethanol, with shaking.cCool the mixture in the tube under a tap. Note the sweetish smell of ethanal (acetaldehyde) at first, then becoming sharper as oxidation continues and forms ethanoic acid (acetic acid).dWhen the reaction has subsided, the mixture can be warmed gently; the smell of ethanoic acid will become more noticeable.Observation The colour of potassium dichromate which isacidified by dilute sulphuric acid will changeits colour from orange to green solutioncontaining chromium (III) ions (Burkett,Brown, Meloni, 2001)The chemical equation shows how potassium changescolor from orange to green
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