Add new section on chemical reactions in main.tex, detailing various types of reactions with definitions and examples. Update main.pdf to reflect these additions.
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main.tex
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main.tex
@@ -1004,8 +1004,8 @@ Lead-free solder & Sn, Cu, Ag & Low melting, no lead toxicity & Electronics \\
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Pewter & Sn (85-99\%), Sb, Cu & Soft, silvery, malleable & Decorative items \\
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Babbitt metal & Sn, Sb, Cu & Low friction, soft & Bearing surfaces \\
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Type metal & Pb, Sn, Sb & Expands on cooling & Printing type \\
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Wood's metal & Bi, Pb, Sn, Cd & Very low melting (70°C) & Fire sprinklers, fuses \\
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Rose's metal & Bi, Pb, Sn & Low melting (98°C) & Fusible alloys \\
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Wood's metal & Bi, Pb, Sn, Cd & Very low melting (70$^\circ$C) & Fire sprinklers, fuses \\
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Rose's metal & Bi, Pb, Sn & Low melting (98$^\circ$C) & Fusible alloys \\
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Nichrome & Ni (80\%), Cr (20\%) & High electrical resistance, heat-resistant & Heating elements \\
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Monel metal & Ni (67\%), Cu (30\%) & Corrosion-resistant, strong & Marine, chemical \\
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Invar & Fe (64\%), Ni (36\%) & Very low thermal expansion & Precision instruments \\
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@@ -1031,6 +1031,487 @@ Bell metal & Cu (78\%), Sn (22\%) & Resonant, hard & Bells, cymbals \\
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\section{Reactions}
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\subsection{Types of reactions}
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\subsubsection{Combination reaction (Synthesis reaction)}
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\textbf{Definition:} Two or more substances combine to form a single product.
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\textbf{General form:} \ce{A + B -> AB}
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\textbf{Examples:}
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\begin{itemize}
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\item Formation of water: \ce{2H2 + O2 -> 2H2O}
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\item Formation of ammonia: \ce{N2 + 3H2 -> 2NH3}
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\item Metal oxide formation: \ce{2Mg + O2 -> 2MgO}
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\item Salt formation: \ce{2Na + Cl2 -> 2NaCl}
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\end{itemize}
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\subsubsection{Decomposition reaction}
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\textbf{Definition:} A single compound breaks down into two or more simpler substances.
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\textbf{General form:} \ce{AB -> A + B}
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\textbf{Examples:}
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\begin{itemize}
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\item Thermal decomposition of calcium carbonate: \ce{CaCO3 ->[heat] CaO + CO2 ^}
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\item Electrolysis of water: \ce{2H2O ->[electrolysis] 2H2 ^ + O2 ^}
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\item Decomposition of hydrogen peroxide: \ce{2H2O2 ->[MnO2] 2H2O + O2 ^}
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\item Decomposition of potassium chlorate: \ce{2KClO3 ->[heat] 2KCl + 3O2 ^}
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\end{itemize}
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\subsubsection{Displacement reaction (Substitution reaction)}
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\textbf{Definition:} One element replaces another element in a compound.
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\textbf{General form:} \ce{A + BC -> AC + B}
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\textbf{Examples:}
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\begin{itemize}
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\item Zinc displacing hydrogen: \ce{Zn + 2HCl -> ZnCl2 + H2 ^}
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\item Chlorine displacing bromine: \ce{Cl2 + 2NaBr -> 2NaCl + Br2}
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\item Magnesium displacing copper: \ce{Mg + CuSO4 -> MgSO4 + Cu}
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\item Iron displacing copper: \ce{Fe + CuSO4 -> FeSO4 + Cu}
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\end{itemize}
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\subsubsection{Double displacement reaction (Metathesis reaction)}
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\textbf{Definition:} Exchange of ions between two compounds.
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\textbf{General form:} \ce{AB + CD -> AD + CB}
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\textbf{Examples:}
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\begin{itemize}
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\item Precipitation: \ce{AgNO3 + NaCl -> AgCl v + NaNO3}
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\item Neutralization: \ce{HCl + NaOH -> NaCl + H2O}
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\item Formation of barium sulfate: \ce{BaCl2 + H2SO4 -> BaSO4 v + 2HCl}
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\end{itemize}
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\subsubsection{Redox reaction (Oxidation-reduction reaction)}
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\textbf{Definition:} Transfer of electrons between species, involving change in oxidation states.
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\textbf{Oxidation:} Loss of electrons, increase in oxidation number.
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\textbf{Reduction:} Gain of electrons, decrease in oxidation number.
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\textbf{Examples:}
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\begin{itemize}
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\item Combustion: \ce{C + O2 -> CO2}
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\item Permanganate oxidation: \ce{2KMnO4 + 5H2C2O4 + 3H2SO4 -> K2SO4 + 2MnSO4 + 10CO2 ^ + 8H2O}
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\item Dichromate oxidation: \ce{K2Cr2O7 + 14HCl -> 2KCl + 2CrCl3 + 3Cl2 ^ + 7H2O}
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\item Zinc-copper cell: \ce{Zn + Cu^2+ -> Zn^2+ + Cu}
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\end{itemize}
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\subsubsection{Acid-base reaction (Neutralization)}
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\textbf{Definition:} Reaction between an acid and a base to produce salt and water.
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\textbf{General form:} \ce{Acid + Base -> Salt + Water}
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\textbf{Examples:}
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\begin{itemize}
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\item Strong acid-strong base: \ce{HCl + NaOH -> NaCl + H2O}
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\item Weak acid-strong base: \ce{CH3COOH + NaOH -> CH3COONa + H2O}
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\item Dibasic acid: \ce{H2SO4 + 2KOH -> K2SO4 + 2H2O}
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\item Carbonate with acid: \ce{Na2CO3 + 2HCl -> 2NaCl + H2O + CO2 ^}
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\end{itemize}
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\subsubsection{Precipitation reaction}
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\textbf{Definition:} Formation of an insoluble solid (precipitate) from aqueous solutions.
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\textbf{Examples:}
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\begin{itemize}
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\item Silver chloride: \ce{Ag+ + Cl- -> AgCl v} (white precipitate)
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\item Lead iodide: \ce{Pb^2+ + 2I- -> PbI2 v} (yellow precipitate)
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\item Iron(III) hydroxide: \ce{Fe^3+ + 3OH- -> Fe(OH)3 v} (brown precipitate)
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\item Copper(II) hydroxide: \ce{Cu^2+ + 2OH- -> Cu(OH)2 v} (blue precipitate)
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\end{itemize}
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\subsection{Organic reactions}
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\subsubsection{Halogenation reaction}
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\textbf{Definition:} Introduction of halogen atoms (F, Cl, Br, I) into organic molecules.
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\textbf{Free radical halogenation (alkanes):}
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\begin{itemize}
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\item Chlorination of methane: \ce{CH4 + Cl2 ->[UV light] CH3Cl + HCl}
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\item Further substitution: \ce{CH3Cl + Cl2 -> CH2Cl2 + HCl}
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\item Bromination of ethane: \ce{C2H6 + Br2 ->[UV light] C2H5Br + HBr}
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\end{itemize}
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\textbf{Electrophilic halogenation (aromatic):}
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\begin{itemize}
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\item Bromination of benzene: \ce{C6H6 + Br2 ->[FeBr3] C6H5Br + HBr}
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\item Chlorination of benzene: \ce{C6H6 + Cl2 ->[AlCl3] C6H5Cl + HCl}
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\item Iodination of benzene: \ce{C6H6 + I2 ->[HNO3] C6H5I + HI}
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\end{itemize}
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\textbf{Addition halogenation (alkenes):}
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\begin{itemize}
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\item Bromination of ethene: \ce{C2H4 + Br2 -> C2H4Br2}
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\item Test for unsaturation: Decolorization of bromine water
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\item Chlorination of propene: \ce{C3H6 + Cl2 -> C3H6Cl2}
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\end{itemize}
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\subsubsection{Nucleophilic substitution}
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\textbf{Definition:} Replacement of a leaving group by a nucleophile.
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\textbf{S$_{\mathbf{N}}$1 mechanism (unimolecular):}
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\begin{itemize}
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\item Two-step process via carbocation intermediate
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\item Rate depends only on substrate concentration
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\item Favored by tertiary halides and polar solvents
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\item Example: \ce{(CH3)3CBr + H2O -> (CH3)3COH + HBr}
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\end{itemize}
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\textbf{S$_{\mathbf{N}}$2 mechanism (bimolecular):}
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\begin{itemize}
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\item One-step process with backside attack
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\item Rate depends on both substrate and nucleophile concentration
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\item Favored by primary halides and aprotic solvents
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\item Inversion of configuration (Walden inversion)
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\item Example: \ce{CH3Br + OH- -> CH3OH + Br-}
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\end{itemize}
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\textbf{Common nucleophiles:}
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\begin{itemize}
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\item Hydroxide (OH$^-$): Forms alcohols
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\item Alkoxide (RO$^-$): Forms ethers
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\item Cyanide (CN$^-$): Forms nitriles
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\item Ammonia (NH$_3$): Forms amines
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\item Water (H$_2$O): Forms alcohols (weak nucleophile)
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\end{itemize}
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\subsubsection{Nucleophilic addition}
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\textbf{Definition:} Addition of a nucleophile to a carbonyl group.
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\textbf{Examples:}
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\begin{itemize}
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\item Cyanohydrin formation: \ce{CH3CHO + HCN -> CH3CH(OH)CN}
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\item Grignard addition: \ce{CH3MgBr + CH2O -> CH3CH2OH} (after hydrolysis)
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\item Bisulfite addition: \ce{RCHO + NaHSO3 -> RCH(OH)SO3Na}
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\end{itemize}
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\subsubsection{Electrophilic addition}
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\textbf{Definition:} Addition of an electrophile to a multiple bond.
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\textbf{Examples:}
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\begin{itemize}
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\item Hydrohalogenation: \ce{C2H4 + HBr -> C2H5Br}
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\item Markovnikov's rule: H adds to carbon with more H atoms
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\item Hydration: \ce{C2H4 + H2O ->[H+] C2H5OH}
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\item Addition of sulfuric acid: \ce{C2H4 + H2SO4 -> C2H5OSO3H}
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\end{itemize}
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\subsubsection{Elimination reaction}
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\textbf{Definition:} Removal of atoms or groups to form multiple bonds.
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\textbf{Dehydrohalogenation (E1 and E2):}
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\begin{itemize}
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\item E2 mechanism: \ce{C2H5Br + KOH ->[alcohol, heat] C2H4 ^ + KBr + H2O}
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\item Zaitsev's rule: Major product is more substituted alkene
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\item E1 mechanism: Two-step via carbocation
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\end{itemize}
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\textbf{Dehydration of alcohols:}
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\begin{itemize}
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\item Ethanol dehydration: \ce{C2H5OH ->[H2SO4, heat] C2H4 ^ + H2O}
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\item Intramolecular (forms alkene) vs intermolecular (forms ether)
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\end{itemize}
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\subsubsection{Oxidation reactions}
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\textbf{Oxidation of alcohols:}
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\begin{itemize}
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\item Primary to aldehyde: \ce{RCH2OH ->[oxidation] RCHO ->[oxidation] RCOOH}
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\item Secondary to ketone: \ce{R2CHOH ->[oxidation] R2CO}
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\item Tertiary alcohols: Resistant to oxidation
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\item Oxidizing agents: \ce{K2Cr2O7/H2SO4}, \ce{KMnO4}, \ce{CrO3}
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\end{itemize}
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\textbf{Oxidation of aldehydes:}
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\begin{itemize}
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\item To carboxylic acid: \ce{RCHO ->[oxidation] RCOOH}
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\item Mild oxidizing agents work (e.g., Tollens' reagent, Fehling's reagent)
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\end{itemize}
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\subsubsection{Reduction reactions}
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\textbf{Reduction of carbonyl compounds:}
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\begin{itemize}
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\item Aldehyde to primary alcohol: \ce{RCHO ->[reduction] RCH2OH}
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\item Ketone to secondary alcohol: \ce{R2CO ->[reduction] R2CHOH}
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\item Reducing agents: \ce{LiAlH4}, \ce{NaBH4}, \ce{H2/Pt}
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\end{itemize}
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\textbf{Reduction of carboxylic acids:}
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\begin{itemize}
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\item To primary alcohol: \ce{RCOOH ->[LiAlH4] RCH2OH}
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\item Requires strong reducing agent
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\end{itemize}
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\subsubsection{Condensation reactions}
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\textbf{Definition:} Combination of molecules with elimination of small molecule (usually water).
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\textbf{Esterification:}
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\begin{itemize}
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\item Fischer esterification: \ce{RCOOH + R-OH <=>[H+] RCOOR + H2O}
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\item Reversible reaction, equilibrium can be shifted
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\end{itemize}
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\textbf{Aldol condensation:}
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\begin{itemize}
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\item Self-condensation of aldehydes: \ce{2CH3CHO ->[OH-] CH3CH(OH)CH2CHO}
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\item Followed by dehydration: \ce{CH3CH(OH)CH2CHO -> CH3CH=CHCHO + H2O}
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\end{itemize}
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\subsubsection{Hydrolysis reactions}
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\textbf{Ester hydrolysis:}
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\begin{itemize}
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\item Acidic: \ce{RCOOR + H2O <=>[H+] RCOOH + R-OH}
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\item Basic (saponification): \ce{RCOOR + NaOH -> RCOONa + R-OH}
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\end{itemize}
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\textbf{Amide hydrolysis:}
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\begin{itemize}
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\item Acidic: \ce{RCONH2 + H2O + HCl ->[heat] RCOOH + NH4Cl}
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\item Basic: \ce{RCONH2 + NaOH ->[heat] RCOONa + NH3 ^}
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\end{itemize}
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\subsection{Named reactions and tests}
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\subsubsection{Silver mirror reaction (Tollens' test)}
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\textbf{Purpose:} Test for aldehydes; distinguishes aldehydes from ketones.
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\textbf{Reagent:} Tollens' reagent - ammoniacal silver nitrate solution \ce{[Ag(NH3)2]+}
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\textbf{Principle:} Aldehydes are oxidized to carboxylic acids while silver ions are reduced to metallic silver, forming a silver mirror on the test tube.
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\textbf{Preparation of reagent:}
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\begin{itemize}
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\item \ce{AgNO3 + NaOH -> AgOH v + NaNO3}
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\item \ce{AgOH + 2NH3 -> [Ag(NH3)2]OH} (soluble complex)
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\end{itemize}
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\textbf{Reaction with aldehyde:}
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\begin{itemize}
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\item \ce{RCHO + 2[Ag(NH3)2]+ + 2OH- -> RCOO- + 2Ag v + 4NH3 + H2O}
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\item Formaldehyde: \ce{HCHO + 4[Ag(NH3)2]+ + 4OH- -> CO3^2- + 4Ag v + 8NH3 + 2H2O}
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\item Glucose (reducing sugar): \ce{C6H12O6 + 2[Ag(NH3)2]+ + 2OH- -> C6H12O7 + 2Ag v + 4NH3}
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\end{itemize}
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\textbf{Observation:} Silver mirror forms on the inner surface of the test tube (positive test).
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\textbf{Note:} Ketones do not give this reaction. Some $\alpha$-hydroxy ketones may give weakly positive results.
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\subsubsection{Fehling's test (Benedict's test)}
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\textbf{Purpose:} Test for reducing sugars and aldehydes.
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\textbf{Reagent:} Fehling's solution (mixture of Fehling's A and B)
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\begin{itemize}
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\item Fehling's A: Copper(II) sulfate solution \ce{CuSO4}
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\item Fehling's B: Alkaline sodium potassium tartrate solution (Rochelle salt)
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\end{itemize}
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\textbf{Principle:} Aldehydes reduce Cu$^{2+}$ (blue) to Cu$_2$O (red-brown precipitate).
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\textbf{Reaction:}
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\begin{itemize}
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\item \ce{RCHO + 2Cu^2+ + 5OH- ->[heat] RCOO- + Cu2O v + 3H2O}
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\item With glucose: \ce{C6H12O6 + 2Cu^2+ + 5OH- -> C6H12O7 + Cu2O v + 3H2O}
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\end{itemize}
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\textbf{Observation:} Blue solution turns to red-brown precipitate of cuprous oxide.
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\textbf{Benedict's reagent:} Similar test using copper citrate complex instead of tartrate.
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\subsubsection{Iodine clock reaction}
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\textbf{Purpose:} Demonstration of reaction kinetics and reaction mechanisms.
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\textbf{Principle:} A sudden color change occurs after a predictable time period, demonstrating the relationship between reaction rate and concentration.
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\textbf{Common version (Landolt reaction):}
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\begin{itemize}
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\item Reaction A (slow): \ce{H2O2 + 2I- + 2H+ -> I2 + 2H2O}
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\item Reaction B (fast): \ce{I2 + 2S2O3^2- -> 2I- + S4O6^2-}
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\item When thiosulfate is consumed, free iodine reacts with starch indicator
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\item \ce{I2 + starch -> blue complex}
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\end{itemize}
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\textbf{Alternative version (Dushman reaction):}
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\begin{itemize}
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\item \ce{IO3- + 3HSO3- -> I- + 3SO4^2- + 3H+} (slow)
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\item \ce{IO3- + 5I- + 6H+ -> 3I2 + 3H2O} (fast, when HSO$_3^-$ depleted)
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\end{itemize}
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\textbf{Observation:} Solution remains colorless for a fixed time, then suddenly turns deep blue.
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\textbf{Variables affecting clock time:}
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\begin{itemize}
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\item Concentration of reactants
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\item Temperature
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\item Presence of catalysts
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\end{itemize}
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\subsubsection{Biuret test}
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\textbf{Purpose:} Test for proteins and peptide bonds; detects presence of peptide linkages.
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\textbf{Reagent:} Biuret reagent (copper sulfate in alkaline solution)
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\begin{itemize}
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\item \ce{CuSO4} in dilute \ce{NaOH} solution
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\end{itemize}
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\textbf{Principle:} Peptide bonds form a colored complex with Cu$^{2+}$ ions in alkaline solution.
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\textbf{Reaction:} Copper ions coordinate with nitrogen atoms of peptide bonds, forming a violet-purple complex.
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\textbf{Named after:} Biuret \ce{H2N-CO-NH-CO-NH2}, the simplest compound that gives this test.
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\textbf{Observation:}
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\begin{itemize}
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\item Negative (no protein): Blue color (from Cu$^{2+}$ ions)
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\item Positive (protein present): Violet to purple color
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\item Intensity depends on number of peptide bonds
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\end{itemize}
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\textbf{Requirements:}
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\begin{itemize}
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\item At least two peptide bonds required for positive test
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\item Single amino acids do not give positive result
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\item Dipeptides give weak positive result
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\item Tripeptides and proteins give strong positive result
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\end{itemize}
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\textbf{Application:}
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\begin{itemize}
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\item Qualitative test for proteins
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\item Semi-quantitative determination of protein concentration
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\item Used in biochemistry and food analysis
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\end{itemize}
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\subsubsection{Lucas test}
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\textbf{Purpose:} Distinguish between primary, secondary, and tertiary alcohols.
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\textbf{Reagent:} Lucas reagent (anhydrous \ce{ZnCl2} in concentrated \ce{HCl})
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\textbf{Principle:} Alcohols react with HCl in presence of \ce{ZnCl2} to form alkyl chlorides (insoluble, appears as cloudiness).
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\textbf{Reactions:}
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\begin{itemize}
|
||||
\item \ce{ROH + HCl ->[ZnCl2] RCl + H2O}
|
||||
\item Rate: Tertiary > Secondary > Primary
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Observations:}
|
||||
\begin{itemize}
|
||||
\item Tertiary alcohol: Immediate cloudiness (turbidity)
|
||||
\item Secondary alcohol: Cloudiness within 5-10 minutes
|
||||
\item Primary alcohol: No reaction at room temperature
|
||||
\end{itemize}
|
||||
|
||||
\subsubsection{Diazotization reaction}
|
||||
|
||||
\textbf{Purpose:} Formation of diazonium salts from primary aromatic amines.
|
||||
|
||||
\textbf{Reagent:} Sodium nitrite (\ce{NaNO2}) and dilute \ce{HCl} at 0-5$^\circ$C
|
||||
|
||||
\textbf{Reaction:}
|
||||
\begin{itemize}
|
||||
\item \ce{C6H5NH2 + NaNO2 + 2HCl ->[cold] C6H5N2+Cl- + NaCl + 2H2O}
|
||||
\item Temperature must be kept low to prevent decomposition
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Applications:}
|
||||
\begin{itemize}
|
||||
\item Azo dye synthesis (coupling with phenols or aromatic amines)
|
||||
\item Sandmeyer reaction (replacement of diazonium group)
|
||||
\item Gattermann reaction
|
||||
\end{itemize}
|
||||
|
||||
\subsubsection{Friedel-Crafts reactions}
|
||||
|
||||
\textbf{Friedel-Crafts alkylation:}
|
||||
\begin{itemize}
|
||||
\item \ce{C6H6 + RCl ->[AlCl3] C6H5R + HCl}
|
||||
\item Introduces alkyl group onto aromatic ring
|
||||
\item Catalyst: \ce{AlCl3} or \ce{FeCl3}
|
||||
\item Problem: Polyalkylation and rearrangement
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Friedel-Crafts acylation:}
|
||||
\begin{itemize}
|
||||
\item \ce{C6H6 + RCOCl ->[AlCl3] C6H5COR + HCl}
|
||||
\item Introduces acyl group onto aromatic ring
|
||||
\item More controlled than alkylation (no polyacylation)
|
||||
\item Forms ketones
|
||||
\end{itemize}
|
||||
|
||||
\subsubsection{Kolbe's reaction (Kolbe-Schmitt reaction)}
|
||||
|
||||
\textbf{Purpose:} Synthesis of salicylic acid from phenol.
|
||||
|
||||
\textbf{Reaction:}
|
||||
\begin{itemize}
|
||||
\item \ce{C6H5OH + NaOH -> C6H5ONa + H2O}
|
||||
\item \ce{C6H5ONa + CO2 ->[heat, pressure] C6H4(OH)COONa} (sodium salicylate)
|
||||
\item \ce{C6H4(OH)COONa + HCl -> C6H4(OH)COOH + NaCl} (salicylic acid)
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Conditions:} High pressure (5-7 atm), 125-130$^\circ$C
|
||||
|
||||
\textbf{Application:} Industrial production of aspirin (acetylsalicylic acid)
|
||||
|
||||
\subsubsection{Cannizzaro reaction}
|
||||
|
||||
\textbf{Purpose:} Disproportionation of aldehydes lacking $\alpha$-hydrogen.
|
||||
|
||||
\textbf{Principle:} In strong base, one aldehyde molecule is oxidized to carboxylate, another is reduced to alcohol.
|
||||
|
||||
\textbf{Reaction:}
|
||||
\begin{itemize}
|
||||
\item \ce{2RCHO + NaOH ->[no alpha-H] RCOONa + RCH2OH}
|
||||
\item Example: \ce{2C6H5CHO + NaOH -> C6H5COONa + C6H5CH2OH}
|
||||
\item Formaldehyde: \ce{2HCHO + NaOH -> HCOONa + CH3OH}
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Requirement:} Aldehyde must lack $\alpha$-hydrogen atoms.
|
||||
|
||||
\subsubsection{Haloform reaction}
|
||||
|
||||
\textbf{Purpose:} Test for methyl ketones; produces haloform.
|
||||
|
||||
\textbf{Reagent:} Halogen (\ce{I2}, \ce{Br2}, or \ce{Cl2}) in alkaline solution
|
||||
|
||||
\textbf{Reaction:}
|
||||
\begin{itemize}
|
||||
\item \ce{CH3COR + 3I2 + 4NaOH -> RCOONa + CHI3 v + 3NaI + 3H2O}
|
||||
\item Iodoform (\ce{CHI3}): Yellow precipitate with characteristic odor
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Positive test:}
|
||||
\begin{itemize}
|
||||
\item Methyl ketones: \ce{R-CO-CH3}
|
||||
\item Acetaldehyde: \ce{CH3CHO}
|
||||
\item Ethanol: \ce{CH3CH2OH} (oxidized to acetaldehyde first)
|
||||
\end{itemize}
|
||||
|
||||
\textbf{Iodoform test:} Specific for compounds with \ce{CH3CO-} or \ce{CH3CH(OH)-} structure.
|
||||
|
||||
\section{Hydrocarbons and their Halogen derivatives}
|
||||
|
||||
\section{Alicyclic compounds and aromatic compounds}
|
||||
|
||||
Reference in New Issue
Block a user