nucleophiles and electrophilic

• What are haloalkanes also known as?

  Halogenoalkanes
• Why are haloalkanes considered valuable synthetic compounds?

  They can be made directly from alkanes and have easily replaceable halogen atoms
• What are the structural features of haloalkanes?

  • Contain at least one halogen atom
  • Halogen atoms can be fluorine, chlorine, bromine, or iodine
  • Halogen can be primary (1º), secondary (2º), or tertiary (3º)
• What is a primary halogenoalkane?

  A primary halogenoalkane has the halogen bonded to a carbon attached to one other carbon
• How does a secondary halogenoalkane differ from a primary halogenoalkane?

  A secondary halogenoalkane has the halogen bonded to a carbon attached to two other carbons
• What characterizes a tertiary halogenoalkane?

  A tertiary halogenoalkane has the halogen bonded to a carbon attached to three other carbons
• What effect do halogen atoms have on the carbon chain?

  Halogen atoms are electronegative and create polarized bonds, making the carbon a reactive center
• What are the key features of substitution reactions involving haloalkanes?

  • Haloalkanes are attacked by nucleophilic reagents
  • The halide ion is substituted by the nucleophile
  • General reaction scheme: R-X + Nu- → R-Nu + X-
• What happens when haloalkanes react with hydroxide ions?

  They undergo nucleophilic substitution to form alcohols
• What is the product of the reaction between chloroethane and sodium hydroxide?

  Ethanol and sodium chloride
• What role does the hydroxide ion play in the reaction with haloalkanes?

  The hydroxide ion acts as the nucleophile
• What is the result of nucleophilic substitution with cyanide ions on haloalkanes?

  It produces nitriles
• What is the general reaction for cyanide ion substitution with haloalkanes?

  KCN + CH3CH2Br → CH3CH2CN + KBr
• How can nitriles be further processed after their formation?

  Nitriles can be reduced to amines using hydrogen and a nickel catalyst
• What are the steps in the mechanism of nucleophilic substitution with cyanide ions?

  1. Cyanide ion attacks the partially positive carbon
  2. Bromine leaves as a bromide ion
  3. Final product is a nitrile
• What is the product of the reaction between ammonia and bromoethane?

  Ethylamine and hydrogen bromide
• How does the mechanism of nucleophilic substitution vary with haloalkanes?

  • Mechanism depends on whether the haloalkane is 1º, 2º, or 3º
  • Different steric hindrance affects the reaction pathway
• what are electrophiles

  Electrophiles are electron-deficient species that can accept electron pairs from electron-rich species. Carbocations and carbonyl compounds are two examples. A nucleophile is an electron-rich species that donates electron pairs to electron-deficient species.
• what are some examples of electrophiles?

  Hydronium ion (H3O+, from Bronsted acids), boron trifluoride (BF3), aluminium chloride (AlCl3), and the halogen molecules fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I) are examples of electrophiles (I2).
• how electrophiles formed


  They are formed due to differences in electronegativity. Most common example occurs in halogenalkanes, where the halide bonded to the carbon is more electronegative than carbon. So it attracts the bonding pair of electrons to itself leaving the carbon with less electrons. It becomes an electrophile.
• Are electrophiles polar or nonpolar?


  Electrophiles can be challenging to recognize because their partial positive charge is hidden in polar bonds and/or resonance. Allkyl halides and carbonyl groups are useful electrophiles for synthetic organic chemistry.
• Are halogenoalkanes electrophiles?


  But haloalkane is an electron deficient species (halogens are electronegative, so they have electron withdrawing effect), so it will not undergo electrophilic substitution rather it may undergo nucleophilic substitution.

  
• what is the difference between primary,secondary and third halogenoalkane halogenoalkanes electrophiles?


  In primary halogenoalkanes, only one carbon atom is attached to the halogen-containing carbon. In secondary halogenoalkanes, two carbon atoms are attached, and in tertiary halogenoalkanes, three carbon atoms are attached.

  
• What is the electrophilic addition reaction of an alkene?


  Instead of a substitution, alkenes undergo electrophilic addition, a reaction in which a two-component reactant adds across the double bond. The reaction begins with an electrophilic attack by the double bond onto the reactant which produces a carbocation that then undergoes nucleophilic attack.
• What is meant by bond enthalpy?


  Bond enthalpy (which is also known as bond-dissociation enthalpy, average bond energy, or bond strength) describes the amount of energy stored in a bond between atoms in a molecule.
• what is high electron density


  Electron density: An atom or group with higher electron density means some aspect of molecular structure (such as resonance or inductive effects) is shifting negative charge towards this spot in the molecule.