Hydrocarbon reactions

Three important reactions of alkanes

combustion, halogenation, dehydrogenation

Combustion of alkane

burn an alkane in oxygen to make carbon dioxide and water

gen eq of combustion of alkane

C_nH_2n+2  +       O₂ à  nCO₂  + (n+1)H₂O

gen eq of alkane combustion example methane

  CH₄ (g)  +  2O₂ (g) à CO₂ (g)  + 2H₂O (g)

Halogenation alkane

Substituting one hydrogen for one halogen atom (F,Cl,Br,I), needs UV light to catalyse the reaction

Halogenation of alkanes gen eq

  C_nH_2n+2  +  X₂  à  C_nH_2n+1X + HX

halogenation of alkane: bromination of ethane produces bromoethane

•Bromination of ethane produces bromoethane

  CH₃-CH₃  +  Br₂  à  CH₃-CH₂-Br  + HBr

•For a second substitution, treat again with halogen

   CH₃-CH₂-Br  +  Br₂  à  Br-CH₂-CH₂-Br  + HBr

•May continue to substitute until all hydrogens are replaced by halogens

reaction of alkane dehydrogenation

removing heat from hydrogen gas from an alkane, produces alkene, needs heat and catalyst

dehydrogenation fo an alkane usage

oil refining industry to manipulate molecules

dehydrogenation of alkane gen reaction

  C_nH_2n+2  à  C_nH_2n  +  H₂

Dehydrogenation of propane produces ___and eq

•Dehydrogenation of propane produces propene

  CH₃-CH₂-CH₃  à  CH₃-CH=CH₂  +  H₂

Reaction of alkene

combustion, addition, reduction, oxidation, halogenation, hydrohalogenation, hydration, polymerisation

Alkene combustion

burn in oxygen gas and produces carbon dioxide and water

addition alkene-most common nd useful?

yes common and usefulm break the double bond and use thos electrons to bond with other atoms

examples of addition of alkene: reduction, halogenation

reduction-add hydrogen/oxidation where add oxygen halogenation add CL2 or B2

examples of addition of alkene: hydrohalogenation, hydration, polymerisation

hydrohalogenation-add HCL, HBR, hydration add water, polymerisation, add monomer

reduction of alkene

loss of gain of hydrogen atoms, catalytic reduction of alkenes, is also called hydrogenation, needs mateal catalyst like Pd, Al, Pt, Ni

gen eq of reduction of alkene

•alkene  +  H₂ (g)  à  alkane 

alkene reduction metal catalyst and example

oxidation of alkene

to increase the oxygen content of a molecule

Transiton metal oxides are good oxidising agents for Alkenes?

yes transition metal oxides are good oxidising agents

oxidising agents for alkene in lab

•permanganate (MnO₄^-) goes from purple to brown (MnO₂)

•dichromate (Cr₂O₇^2-) goes from orange to green (Cr³⁺)

halogenation alkene

chlorine and bromine gas only because fluorine is too violent and iodine wont react

result of halogenation of alkene

break the alkene’s double bond and break the halogen-to-halogen bond, results in haloalkane (alkyl halide)

alkene hydrohalogenation

HX adds to symmetric alkene or HX add to an assymetric alkene

Hydration alkene

use Markovnikov’s rule to predict produce, us acid catalyst to star (HCL, H2SO4)

polymerisation of alkene

chan-growth, joining monomer units without loss of atoms

example of polymerisation of an alkene

polyethylene formation

monomer is an alkene, polymer is an alkane

requires catalyst

 

ethene (ethylene)                             polyethylene

Reaction of aromatic hydrocarbonds

combustion, substitution

substitution of aromatic hydrocarbon

1 or more of hydrogens around benzene ring can be replaced by another atom or group, will not do additon and break aromatic ring

substitution reactions-replacing a hydrogen atom of aromatic hydrocarbon:halogenation, nitration, sulfonation

halogenation-add Cl, Br, I to aromatic ring, nitration-add NO2 group, sulfonation-add SO3H group

substituion reactions replacing a hydrogen atom aromatic hydrocarbon: alkylation, acylation

alkylation-add R group where R=CH3, CH2Ch3, acylation-add COR group where C is double bonded to O