haloalkanes Flashcards
Alkyl Halides
derivative of alkane by replacing one hydrogen atoms by halogen atom. Monohalo derivative.
ethylidene chloride’s formula
1, 1- Dichloroethane geminal dihalides
ethylene dichloride’s formula
1, 2-Dichloroethane vicinal dihalides
what is the product when we react alcohol with HX ?
RX + Water
What is the product when alcohol reacts with HX according to SN1 mechanism?
water gets loss and carbocation is formed (rearrangement if possible) in the first step. In the second step Halide ion reacts over it and we get alkyl halide.
what is the product when alcohol reacts with HX according to SN2 mechanism?
It is a single step reaction so we directly get our products RX and water.
How are phosphorus halides prepared?
red Phosphorus + Halogens
what is the advantage of using phosphorus halides?
carbocations are not formed so no possibility of rearrangement in prior of forming products. so no SN1 mechanism
ROH + PCl 5 =
RCl + POCl 3 + HCl
3ROH + PCl 3 =
3RCl + H 3 PO 3
3ROH + PBr 3=
3RBr +H 3 PO 3
3ROH + PI 3=
3RI + H 3 PO 3
what is the product when alcohol reacts with Thionyl Chloride SOCl 2? ( in the presence of pyridine) and what is the use of pyridine over here?
R-Cl + SO 2 +HCl both are gaseous products so they can escape. Pyridine is used to trap HCl gas so as to form pyridinium chloride. The products are formed with inversion of configuration in presence of pyridine (SN2) and retention of configuration in absence of Pyridine(SN1).
Direct halogenation of Hydrocarbon in presence of U.V light gives? which Halogens are most reactive and least reactive ? which degree hydrogen would replace first? and which Last?
RX +HX.
F 2
I 2
Tertiary hydrogen then secondary hydrogen and then primary hydrogens.
what measures are taken while halogenating with I 2 ?
I 2 is reversible so we use oxidizing agents to oxidize HI formed by HIO 3 or HNO3
what is a finkelstein reaction?
It’s halide exchange, Preparation of Alkyl iodides from chlorides or bromides by using NaI and acetone as solvent.
RX + NaI (acetone)= RI + NaX x=Br, Cl
NaBr or NaCl are insoluble in acetone so can be easily removed.
what is a hunsdiecker reaction?
RCOOAg + X 2 (CCl 4)= RX + AgX + CO 2
X= Br, Cl
Which is the probable mechanism in Hunsdieker reaction?
Free radicle.
what is the first product in Hunsdieker reaction?
Acyl Hypohalite. RCOOX and int his reaction there is involvement of chain reaction.
In Hunsdieker reaction in solvent CCl 4 which halogen gives a better yield?
Br 2 than Cl 2
In Hunsdieker reaction which type of alkyl halide is easily formed or order?
primary alkyl halide then secondary then tertiary.
what if I 2 is used in Hunsdieker reaction? What is that reaction called?
then the product would be an ester.
Birbaum- Simonini reaction
2RCOOAg + I 2 = RCOOR +2AgI+ CO 2
2RCOOH + 2I 2 + (red) Hg 2 O =
2RI + 2CO 2 + HgI 2
If ethyne is the substrate what is the reagent to form vinyl halide? (CH2=CH-Cl)
HCl and CuCl 2
the lower members of alkyl halides are of which physical state ? and Higher members are of?
Gases
colourless sweet smelling liquids.
Alkyl halides are soluble in?
alcohols ether benzene
In isomeric alkyl halides what is the boiling point?
primary> secondary> tertiary
Iodide> bromides> chlorides> fluorides
the reactivity of alkyl halides to form organometallic compounds
alkyl fluorides< alkyl chlorides< alkyl bromides< alkyl iodides
Alkyl organometallic compounds are a good source of?
Carbanions matlab nucleophiles ki factory.
What is the product of reduction of alkyl halides?
Hydrocarbons, alkane
the reagents used for reduction of alkyl halides to alkanes?
(Zn, CH3COOH)( Zn, HCl)( Zn, NaOH)( Zn-Cu alcohol), (aluminium amalgam alcohol)
RX + Alcoholic KOH=
alkene …dehydrohalogenation markownikoffs rules product is the major product.
2RI—>(in presence of light)
R-R + I 2
When the nucleophile is the solvent then the reaction is called
Solvolysis
Nucleophilicity?
reaction of nucleophile with electrophillic carbon
fact related to nucleophilicity and basicity
nucleophilicity increase basicity decreases and
