Can somebody help me with addition reactions and recations of alkenes i dont understand them. also if somebody could go over nucleophillic addition it would be greatly appreciated!
First and foremost:
Addition --- 2 reactants make 1 product Subsitution --- 2 reactants make 2 products Elimination --- 1 reactant makes 2 products
Electrophile = A atom that is attracted to an electron rich centre (e.g. double C=C bond), and accepts a pair of electrons, in order to form a new covalent bond.
Neuclophile = Basically opposite, so attracted to electron deficient centre and donates a pair of electron.
The mechanism for alkenes is that they react with electrophiles. E.g. Halogens or Hydrogen halide. Therefore they are known as electrophillic addition, since only 1 product is produced.
Other reactions of alkenes:
With hydrogen (Hydrogenation), Hydrogen opens up double bonds and makes saturated alkane. Nickel catalyst and 150 degrees Celsius needed.
With halogens, e.g F,Cl, Br, I Halogens add across double bond, opening them UP = Saturated. Halogens would then replace two hydrogens. E.g - F2 would replace two hydrogens in ethene, forming 1,2-difluoroethane.
With steam Produces an alcohol, since OH replaces H. Acid catalyst needed (E.g. - Phosphoric acid)
This is only SOME of the reactions, I would go on, but it will take forever to type. Hope things are starting to be clearer now. Feel free to ask any questions!
Can somebody help me with addition reactions and recations of alkenes i dont understand them. also if somebody could go over nucleophillic addition it would be greatly appreciated!
Guys... If CCl2 has a bond angle of 118 then why does it change so dramatically when you have two lone pairs... I thought if it was V-shaped then it would be 115
For OCR A we have to know how to read the results of mass spec analysis but not actually how these results are brought about So you only have to be able to read the graphs
-The halogen is more electronegative than the Carbon atom and so becomes slightly negative, which induces the carbon atom to become slightly positively charged - electron deficient Carbon atom. This attracts nucleophiles such as OH. The lone pair of electrons from the nucleophile (formed due to heterolytic fission) are attracted and donated to the electron-deficient Carbon atom - this forms a new covalent bond between the Oxygen atom and Carbon atom. The C - Br breaks by heterolytic fission, and the electrons are donated to the halogen forming an ion.
Electrophilic Addition:
-This mechanism occurs during halogenation and halogenoalkane. The halogen is more electronegative and so becomes slightly negatively charged as the electron pair is attracted to the Bromine atom, this induces the Hydrogen atom to become slightly positively charged. The electron pair from the Carbon=Carbon is attracted by the slightly charged hydrogen atom which causes the double bond to break. A new bond forms between the first carbon atom and the hydrogen atom, and so the H - Br bond breaks by heterolytic fission and the electron pair goes to the bromine, forming a bromide (ion), which then reacts with the positively charged carbon atom.
Hey guys I'm really struggling. I think O understand the Hess's cycle but when I'm solving past papers I never seem to solve them. So could someone please explain the hess's cycle? Thanks much appreciated.
Hey guys I'm really struggling. I think O understand the Hess's cycle but when I'm solving past papers I never seem to solve them. So could someone please explain the hess's cycle? Thanks much appreciated.
If you have an example of both Formation + Combustion, I'm happy to help!
Guys... If CCl2 has a bond angle of 118 then why does it change so dramatically when you have two lone pairs... I thought if it was V-shaped then it would be 115
If it has 2 lone pairs and 2 bonding pairs then it ought to have bond angle of 104.5o and it'll be a bent shape.
Hey guys I'm really struggling. I think O understand the Hess's cycle but when I'm solving past papers I never seem to solve them. So could someone please explain the hess's cycle? Thanks much appreciated.
Just to mention, the cycle for Combustion and the route is ALWAYS the same for every combustion-related question. The values just differ from question to question. 1) Begin by forming an equation to form the products. 2) Substitute numbers into the cycle and calculate the Sum of Reactants. 3) As the cycle suggests to form the combustion products you can directly combust the products, we go against this arrow as suggested by the route which needs to be taken - and so, the value of the product changes from NEGATIVE to POSITIVE. Enthalpy change of reactants + products = answer.
Hope that helped, I'll try and find a question for Enthalpy change of Formation.
Just to mention, the cycle for Combustion and the route is ALWAYS the same for every combustion-related question. The values just differ from question to question. 1) Begin by forming an equation to form the products. 2) Substitute numbers into the cycle and calculate the Sum of Reactants. 3) As the cycle suggests to form the combustion products you can directly combust the products, we go against this arrow as suggested by the route which needs to be taken - and so, the value of the product changes from NEGATIVE to POSITIVE. Enthalpy change of reactants + products = answer.
Hope that helped, I'll try and find a question for Enthalpy change of Formation.