Halogenoalkanes Overview

Halogenoalkanes can be formed from alkanes through free-radical substitution in the presence of UV light.

The reaction occurs in three steps: initiation, propagation, and termination.

A red-brown color of bromine vapor is liberated during the reaction, indicating that bromine is being consumed.

<p>An example is propene reacting with fluorine to form 1,2-difluoropropane.</p> Signup and view all the answers

<p>Alkenes react with halogens to form halogenoalkanes in a straightforward addition reaction.</p> Signup and view all the answers

<p>A tertiary (3°) carbocation is formed during the SN1 reaction, considered stable due to the inductive effect from three electron-donating alkyl groups.</p> Signup and view all the answers

<p>The primary product is ethyl amine, CH3CH2NH2.</p> Signup and view all the answers

<p>Higher concentration of 2-chloro-2-methylpropane increases the reaction rate, while lower concentration decreases it.</p> Signup and view all the answers

<p>The reaction of bromoethane with cyanide ion forms propane nitrile and KBr.</p> Signup and view all the answers

<p>The hydroxide ion acts as a base, accepting a proton (H+) to form water.</p> Signup and view all the answers

<p>The rate of the SN2 reaction depends on the concentrations of both the halogenoalkane and the nucleophile.</p> Signup and view all the answers

<p>1-bromo propane + NaOH (in ethanol) → propene + H2O + NaBr.</p> Signup and view all the answers

<p>Bromine's higher electronegativity creates a partial positive charge on carbon, facilitating nucleophilic attack by hydroxide.</p> Signup and view all the answers

<p>Pent-2-ene is the major product because it has two alkyl groups attached to the double bond, stabilizing it.</p> Signup and view all the answers

<p>A secondary amine, specifically isopropyl amine, CH3CH(NH2)CH3, is formed.</p> Signup and view all the answers

<p>2-chloropropane undergoes an SN1 reaction mechanism with cyanide due to the formation of a stable carbocation.</p> Signup and view all the answers

<p>The cyanide ion attacks the carbon atom bonded to the bromine, leading to the breaking of the C-Br bond.</p> Signup and view all the answers

<p>The slow step, or rate-determining step, involves the simultaneous breaking and forming of bonds between the halogenoalkane and nucleophile.</p> Signup and view all the answers

<p>The expected product is the tertiary amine, 2-methyl-2-aminopropane, along with HBr.</p> Signup and view all the answers

<p>Primary halogenoalkanes, like bromoethane, favor the SN2 pathway due to lower steric hindrance compared to secondary or tertiary halogenoalkanes.</p> Signup and view all the answers

<p>The carbon atom becomes partially positive due to the electronegativity of the halogen (like bromine).</p> Signup and view all the answers

<p>A halogenoalkane is an organic compound formed when a hydrogen atom in an alkane is replaced by a halogen.</p> Signup and view all the answers

<p>The general formula for halogenoalkanes is CnH2n+1X, where X represents any halogen.</p> Signup and view all the answers

<p>Halogenoalkanes transition from gas to liquid as the number of carbon atoms increases.</p> Signup and view all the answers

<p>The polarity of the C-X bond leads to dipole-dipole attractions, increasing melting and boiling points.</p> Signup and view all the answers

<p>Iodoethane has the highest melting and boiling point due to its stronger dispersion forces.</p> Signup and view all the answers

<p>A primary halogenoalkane has one alkyl group attached to the carbon containing the halogen.</p> Signup and view all the answers

<p>Electronegativity differences result in bond polarity, with higher differences creating more polar bonds.</p> Signup and view all the answers

<p>Halogenoalkanes exhibit dispersion forces and permanent dipole-dipole attractions due to polar C-X bonds.</p> Signup and view all the answers

<p>The product is an alcohol and HX.</p> Signup and view all the answers

<p>Iodoalkanes undergo hydrolysis the fastest due to the weaker C-I bond, which is easier to break.</p> Signup and view all the answers

<p>Tertiary halogenoalkanes hydrolyze faster than secondary, which hydrolyze faster than primary halogenoalkanes.</p> Signup and view all the answers

<p>CFCs deplete ozone by releasing chlorine free radicals that react with ozone, breaking down O3 into O2.</p> Signup and view all the answers

<p>The main disadvantage is their contribution to ozone layer depletion, which leads to increased UV radiation exposure.</p> Signup and view all the answers

<p>Water is a neutral molecule and a less effective nucleophile compared to the negatively charged OH- ion.</p> Signup and view all the answers

<p>The overall equation is $2 O_3 ightarrow 3 O_2$.</p> Signup and view all the answers

<p>Hydrofluorocarbons (HFCs) can be used as they do not contain chlorine and are less harmful to the ozone layer.</p> Signup and view all the answers

<p>The primary product is 1-fluoropropane (CH3CHFCH2F).</p> Signup and view all the answers

<p>Aqueous hydrogen halides provide a wet environment which does not allow for the in-situ preparation of dry hydrogen halides, making them less effective nucleophiles.</p> Signup and view all the answers

<p>The products formed are halogenoalkane, hydrogen chloride (HCl), and phosphorus oxychloride (POCl3).</p> Signup and view all the answers

<p>SOCl2 acts as a reagent that facilitates the substitution of -OH group in alcohols to form halogenoalkanes.</p> Signup and view all the answers

<p>Dry hydrogen halide should be prepared in-situ to enhance its nucleophilicity.</p> Signup and view all the answers

<p>Mist fumes of HCl gas are observed during the reaction.</p> Signup and view all the answers

<p>Heat is applied to facilitate the reaction and increase the substitution efficiency of -OH group with chlorine.</p> Signup and view all the answers

<p>Hydrogen chloride (HCl) reacts with propene to yield 2-chloro propane as the major product.</p> Signup and view all the answers