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SS 3 Chemistry (1st Term)

Chemistry

AMINES AND AMIDES

AMINES It has a functional group of NH2. GENERAL MOLECULAR FORMULAR/STRUCTURE It has a general molecular formula of RNH2 or structure of              R – N – H H PREPARATION: They are derivatives of ammonia where one or more hydrogen atoms have been replaced by alkyl or aryl groups e.g. RNHz, R2NH.   CLASSIFICATION: Amines can be classified according to alkyl group.   Primary amine with one alkyl group e.g. RNH2 or R                      or                     CH3 H          N          H                      H          N          H Secondary amine with 2 alkyl groups e.g. R2NH or R                      CH3 R          N    or     CH3      N        H H Tertiary amine with 3 alkyl groups e.g. R3N or R                                             CH3 R1      N        R11    or             CH3          N      CH3 Trimethyl amine PHYSICAL PROPERTIES They can dissolve in water. They are gases and liquid. They have fishy odour.   CHEMICAL PROPERTIES As bases they neutralize acids. They dissociate/ionize in… Read More »AMINES AND AMIDES

Chemistry

CARBOHYDRATES

Carbohydrates are naturally occurring organic compounds containing carbon, hydrogen and oxygenwith oxygen in the ratio 1:2 as in water.  The general molelcular formula of carbohydrates is Cx(H2O)y  or  CxH2yOy.  Carbohydrates are generally polydroxyl aldehydes, ketones or any compound that on hydrolysis yields any of the polyhydroxides.  They are synthesized in green plants by photosynthesis.   CLASSIFICATION OF CARBOHYDRATES Carbohydrate Simple sugar                             Complex sugar (polysaccharides) Monosaacharide           Disacharides                   e.g. starch cellulose e.g. glucose                  e.g sucrose   EVALUATION Define carbohydrates. State one example each of simple sugar and complex sugar.   MONOSAACHARIDES Monosaacharides are simple sugar with three to six carbon atoms per molecule.  The most common and important of these are the ones with six carbon atoms per molecule called the HEXOSES. They have the same molecular formula C6H12O6 but different spatial arrangement.  Examples include glucose, fructose, galatose and mannose.   GLUCOSE (C6H12O6) Glucose, commonly known as grape sugar or… Read More »CARBOHYDRATES

Chemistry

NATURAL AND SYNTHETIC POLYMERS

NATURAL AND SYNTHETIC POLYMERS Polymerisation (addition and condensation) plastics.    Thermosplastic and thermosetting polymers, resins.     Polymer is the final product, macromolecule of high molecular mars.  It consists of a repeating units and its general molecular formula may be represented as [repeating units]n where n is a very large whole number. N.B:-    All polymers are macromolecules, but not all macromolecule but it is not polymeric.   NATURAL POLYMERS These are organic compounds which can be found in living thing e.g. carbohydrates like starch and cellulose and all proteins fats and oils are not large enough to be grouped as giant molecule or polymer.   SYNTHETIC POLYMERS These are called plastics e.g. nylon polythene etc.   EVALUATION State a difference between natural polymers and synthetic polymer with example each. What is another name for synthetic polymer?   POLYMERIZATION This is the process whereby two or more monomers link/join together to form… Read More »NATURAL AND SYNTHETIC POLYMERS

Chemistry

Fats and Oils As Higher Esters

Sources, properties and uses detergents and soaps Structure, their mode and action. Fats and oils belong to a general group of compounds known as lipids. SOURCES Fats are solids that usually come from animals e.g. Tallow (mutton fat).  Oils are liquids that come from plants e.g. vegetable oil, coconut oil etc.  Both fat and oil are esters of the trihydricalkanol(propane -1, 2, 3- triol).   PHYSICAL PROPERTIES Fats have higher melting points due to the presence of higher proportion of esters of saturated fatty acid. Oils have lower melting points because of the presence of esters of unsaturated fatty acid.   CHEMICAL PROPERTIES Hydrogenation of oils. This is carried out in the presence of nickel as catalyst at 1800C to yield margarine.   Saponification: Hydrolysis of fats and oils with canotic alkali yields propane -1, 2, 3- triol and fatty acid          of sodium or potassium.   USES OF FATS AND… Read More »Fats and Oils As Higher Esters

Chemistry

ALKANOIC ACIDS

ALKANOATES General molecular formula, nomenclature,  preparation,  properties and uses.   SOURCES The alkanoic acid or carboxylic acids are also called fatty acids because some of them are found in natural fats and oils.  They contain the functional group called carboxy group.   NOMENCLATURE The IUPAC name of each homologue is obtained by changing the “-e” endind of the corresponding alkane to “-oic” acid e.g. mathanoic, ethanoic etc.   STRUCTURE Alkanoic acid has a general molecular fomular of CnH2n + 1COOH where n > 0. or RCOOH.  Thus it has the following structure. O RC OH   E.g.Ethanoic acid CH3COOH H O H          C       C   H            OH PREPARATION   e.g.Ethanoic acid Ethanoic acid can be prepared by the complete oxidation of ethanol by acidified sodium heptaoxo dichromate (VI) solution.  The oxidation reaction is a two stages of reaction Ethanol oxidized to ethanol; CH3CH2OH             O3         CH3CHO   Ethanol oxidized to… Read More »ALKANOIC ACIDS

Chemistry

ALKANOLS

SOURCES OF ALKANOLS –           From destructive distillation wood. –           From starchy food and sugar   General molecular formular Alkanol is a homologous series with general molecular formular of Cn H2n+1OH or ROH. Or (CnH2n+2O).   Nomenclature The names of alkanols are obtained by substituting “e” in alkanes with “Ol” in alkanol e.g. methanol (CH3OH), ethanol (CH3CH2OH).   Classification The alkanols are classified based on the number of alkyl groups directly linked to the carbon atom holding the hydroxyl group. Primary alkanols (10): It has only one alkyl group attached to the carbon atom that carries the hydroxyl group e.g.                                     H R –       C     OH H OR H          H                                              H H      C          C   OH          or     H     C   OH H          H                                              H Ethanol                                                Methanol Secondary alkanols (20):- They have 2 alkyl groups directly linked with the carbon atom holding the hydroxyl group e.g.     H          H         … Read More »ALKANOLS

Chemistry

AROMATIC HYDROCARBONS

Benzene: Benzene is a typical aromatic compound with molecular formula of C6H6.  It has the structure of: Preparation From coal tar: The destructive distillation of coal produced coal tar which contain      benzene From petreoleum; The dehydrogenated of alkane using valladim (v) oxide (v2O5) as     catalyst at 500oC and 20 atmos give benzene C6H14     V2O2C6H6  +  4H2 The process is known as catalysticreforming . From polymerization of ethyne 3 ( H – C = C – H )           C6H6   Evaluation Describe three (3) ways of preparing benzene. Draw the structure of benzene.   Physical properties It has a pleasant odour. It has boiling point of 80oC. Benzene can dissolve in water. It burns with sooty flame.   Chemical Properties Benzene can undergo both additional reaction and substitutional reaction. Additional Reaction. Hydrogenaton:  Benzene reduces to cyclo-hexane if hydrogen gas is passed through       finely divided mickel at 150oC. Halogenation:  In the presence… Read More »AROMATIC HYDROCARBONS

Chemistry

ALKYNES

Alkynes are the  homologous series of unsaturated hydrocarbon  with a general molecular formua CnH2n-2. Alkynes show a high degree of unsaturation than alkenes, hence,t hey are chemically more reactive than the corresponding alkenes or alkanes. Examples are : H H – C = C – H                           HC  – C =  C- H [ Ethyne.                                               H                 prop-1-yne   ETHYNE Ethyne is the first member of the alkyne series.  It has a molecular formula, C2H2, and a structural formular of HC = CH.   Laboratory Preparation Ethyne is usually prepared in the laboratory by the action of  cold water on calcium carbide.  The reaction is carried out on a heap of sand to prevent the flask from cracking as a result of the large quantity of heat evolved.   Evaluation Write and name all possible structure of hexyne How can you prepare a few jars of ethyne in the laboratory? Nomenclature: … Read More »ALKYNES

Chemistry

Unsaturated Hydrocarbons – Alkenes

UNSATURATED HYDROCARBONS These are hydrocarbons in which carbon atoms join with each other by multiple bonds.  The multiple bond can be double bonds e.g Alkene or triple bonds e.g Alkyne. Ethene2 .Ethyne H – C = C – H                                       H – C = C – H H   H. Alkenes e.gEthene Nomenclature The process of naming in alkene is obtained by substitute “ane” in alkane with ‘ene’ e.g Ethane changes to Ethene, propane to prepene   PREPARATION (Lab. Preparation)  Ethene is prepared by heating ethanol with excess concentrated tetraososulphate VI      acid at 170o C. The acid acts as a dehydrating agent by removing water from the ethanol . Thus the process is called dehydration. The reaction occurs in two stages C2H5OH(aq)  + H2SO4 (aq)                C2H5HSO4 + H2O C2H5HSO4               C2H4+ H2SO4. The overall reaction is represented by the equation . C2H5OH  H2SO4 C2H4+ H2SO4 -H2O Ethene can be prepared through cracking… Read More »Unsaturated Hydrocarbons – Alkenes

Chemistry

Saturated Hydrocarbons

Saturated Hydrocarbons Saturated hydrocarbons are hydrocarbons consisting of  carbon chains with single bond between them  in which carbon joins with another carbon by single covalent bond e.g Alkanes ( like ethane C2H6, propane C3H8 )   H          H                                              HHH   H –   C          C – H                            H – C  –     C –     C – H   H        HHHH   Alkanese.g Methane (CH4)   The alkanes are aliphatic hydrocarbons.  They form homologous series of saturated hydrocarbons with general molecular formular of CnH2n+2   EVALUATION What is saturated hydrocarbons? Name one example of alkanes.   Preparation of  Methane (CH4) Methane is prepared in the laboratory by heating ethanoate salt with corresponding alkalis e.g Sodium ethanoate and soda-lime.   Physical Properties Methane is a colourless and odourless gas It is slightly soluble in water. It is less dense than air It has no action on litmus paper   Chemical Properties. Combustion:- Methane burns… Read More »Saturated Hydrocarbons

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