Halogen Derivatives Flashcards
How are halogen derivatives of hydrocarbons classified?
On the basis of hydrocarbon skeleton to which halogen is attached to giving haloalkanes , haloalkenes, haloarenes and on the basis of number of halogen atom on halogen derivatives giving di try and only halogen compounds
On what basis are monohalogens classified?
On the basis of hybridization of carbon to which halogen is attached and position of halogen atom
What are alkyl halides or haloalkanes
In which halogen atom is attached to so3 hybridized carbon which is a part of the saturated carbon skeleton. Are primary , secondary and tertiary ,
What are allylic halides
Halogens are attached to sp3 hybridized Carbon atom which is attached to a carbon carbon double bond
What are benzylic halide?
Halogen atom is bonded to sp3 carbon which is bonded to an aromatic ring
What is vinyl is halide?
Halogen is bonded to sp2C of alicyclic chain
What is haloalkyne?
Halogen is attached to sp hybridized carbon atom
Aryl halides or haloarenes
Halogen atom is directly bonded to sp2 C of an aromatic ring
How are alkyl halides named?
Named as haloalkanes… naming of alkyl group followed by name of halogen as halide
How are alkyl halides prepared from alcohol?
By replacement of hydroxyl group by halogen atom using 3 ways - 1) halogen acids
2) phosphorus halide 3) thionyl chloride AND from hydrocarbons using addition of hydrogen halide to alkene i.e markonikov rule and peroxide effect
Explain how halogen acid used to make haloalkanes
1) HCl+ Anhy. AlCl3 used for primary and secondary alcohols(LUCAS REAGENT)
2) Conc. HCl used for tertiary alcohols
3)NaBr+H2SO4 used to make HBr which reacts with R-OH to give R-Br
4)NaI + H3PO4 used to make HI which reacts with R-Oh to give R-I
Explain how phosphorus halide used to make haloalkanes
1)PX3 (x= I Br Cl F) reacts with R-OH to make 3R-X + H3PO4
2) PCl5 (Phosphorus pentachloride) reacts with R-OH to give R-Cl+ HCl + POCl3
Explain how thionyl chloride is used to make alkyl chloride
No extra efforts required in this reaction hence preferred
R-OH + SO2Cl2 makes R-Cl + SO2(gas) + HCl (gas)
Explain how addition of hydrogen halide to Allene forms haloalkanes
By MKR rule (classical carbocation mechanism) , peroxide effect and reactivity if HX
How are ALKYL IODIDES prepared easily?
Using alkyl chlorides and bromides with sodium iodide in methanol or acetone solution
What is FINKELSTEIN REACTION?
RCl + NaI—————> RI + NaCl (ppt)
Acetone
How are alkyl fluorides formed
Alkyl bromides and chlorides are heated with metal fluorides like AgF and SbF3
What is SWARTZ REACTION
RCl + AgF——> RF + AgCl(ppt)
What is SANDMEYERS REACTION?
Aryl halides can be prepared by replacement of diazonium salt.
Why are alkyl halides moderately polar compounds?
Halogens are highly electronegative elements in comparison with carbon… hence polarity is developed on both atoms … carbon develops a partial positive charge and halogen develops a partial negative charge. Thus a carbon halogen bond in alkyl halide is a polar covalent bond.
Why from iodine to fluorine bond enthalpy decreases
I to F size decreases
As C-X bond length increases , bond strength decreases because as the size of p-orbital of halogen increases the p-orbital becomes more diffused and extent of overlap with orbital of carbon decreases.
What is the order increasing boiling point of alkyl halide?
RI> RBr> RCl >RF
Increasing atomic mass of halogen due to van der waals force
What happens to boiling points of isomeric alkyl halides?
Boiling point decreases with increased branching as surface area decreases and van der waals forces decrease.
Briefly explain solubility of alkyl halides
1) insoluble in water due to inability of forming hydrogen bonds with water as attraction between alkyl halides is stronger than that of alkyl halides and water
2)soluble in non polar organic solvents
