Halogen Derivatives

Question 1

General formula

Answer 1

C_nH_2n+1X
=> At least 1 Halogen atom bonded to sp³ hybridised C atom
=> C-X bond is polar since X atom more EN than C atom

Question 2

**Physical properties **

1. Predominant IMFOA
2. Solubility in Polar/ non-Polar
3. Density

Answer 2

1. Polar compound (R-X bond polar)
   => pd-pd & id-id
   => B.P of RX > that of corresponding alkane
2. Solubility
   => Despite being polar, poor solubility in H₂O (unable to interact via H bonding)
   => Soluble in non-polar organic solvents (Hexane) (able to interact via id-id interactions)
3. Density
   => F-X and mono CL-X less dense than water
   => I-X and poly subbed CL-X denser than water

Question 3

Preparation of RX
=> 3 ways

Answer 3

1. Alkane
   => Free Radical sub via X₂ and uv light
   => not preferred, FRS has no control, risk of poly sub, multiple pdts
2. Alkene
   => 1 X atom/ molecule: E.A via dry HX, rtp, dark
   => 2 X atom/ molecule: E.A via X₂ in CCL₄, rtp, dark
3. Alcohol
   => Nucleophilic sub 4 ways
   - Dry HX, heat
   - PX₃, ANHYDROUS
   - PCL₅, ANHYDROUS
   - SOCL₂

Question 4

Reactivity of RX

Answer 4

C-X bond is polar as X more EN than C
=> C gains partial +ve (electron deficient)
=> attracts nucleophiles

Question 5

Definition: Nucleophile

Answer 5

Species able to donate an electron pair to an electron deficient atom to form a covalent bond

Question 6

RX with nucleophile

Answer 6

Nucleophilic substitution
=> Mechanism
=> S_N1 vs S_N2
=> substitution of X by Nu

Question 7

RX with Bronsted-Lowry base => proton acceptor

Answer 7

Elimination
=> New π bond formed
=> Alkene formed