Functional Group Chemistry 3 Flashcards
Describe alcohols
Unsaturated or saturated
O = sp3
Act as Nu-
Reactivity controlled by e- rich O
What happens to alcohol boiling point as homologous sequence increases?
Increases
Why do alcohols have unusually high boiling points?
H bonding
What happens to solubility of alcohols as size of alkyl group increases?
Decreases
What is the pKa range of alcohols?
15.5-18.0
What happens to acidity of alcohols as alkyl group increases?
Decreases
What do halogens do to alcohols?
Increase acidity = e- withdrawal
What is the preparation of alcohols?
CO + 2H2 —-> CH3OH
400 degrees
ZnO/CrO3
What are the 3 main ways more complex alcohols are formed?
Hydration of alkenes
Hydrolysis of alkyl halides
Reduction of aldehydes/ketones/esters
What can the aldehyde be reduced to?
Primary alcohol
What can a carboxylic ester be reduced to?
Primary alcohol
What can a carboxylic acid be reduced to?
Primary alcohol
What is a ketone reduced to?
Secondary alcohol
What are aldehydes and ketones reduced by?
Sodium borohydride = NaBH4
OR
Lithium aluminium hydride = LiAlH4
What can acids + esters only be reduced by?
LiAlH4
How can alkoxides be formed?
React ethanol with sodium metal (redox reaction)
OR
Cleavage of haloalkanes by hydroxide
Conversion to haloalkanes
Describe addition of H-X to alcohols
HCl, HBr or HI
Displaces hydroxyl with halogen
Form haloalkane
How is an ester formed from an alcohol?
Acid + alcohol ⇆ ester + H2O
H+ catalyst = H2SO4
What is the equation for acid dehydration?
Acid + alcohol ⇆ ester + H2O
What is the equation for acid hydrolysis?
Ester + H2O ⇆ acid + alcohol
What are alcohols oxidised to?
Aldehydes —-> carboxylic acids
Ketones
What is needed for alcohol oxidation?
Metal salts
Describe phenols
Planar
C-O bond distance shorter
Unusual H bonding
What does the hydroxyl group of phenols allow?
H bonding to other phenol molecules in H2O
What does the H bonding in phenols do?
Raises melting point
Increases solubility in H2O
What is phenoxide stabilised by?
Resonance
What do phenols have compared to alcohols?
Higher acidity
Describe haloalkanes
Act as E+
Reactivity controlled by e- poor C
C can be attacked by Nu-
Halogen can leave with e- pair
What does it mean that the C-halogen bond is polar?
Bonded C has partial positive charge
What does a haloalkane have compared to alkane?
Higher boiling point
= greater polarizability of C-X bond
What is the density of liquid haloalkanes compared to hydrocarbons?
Higher
How are haloalkanes prepared?
Free radical substitution of alkanes
Electrophilic addition to alkenes
Halogenation of alcohols
Halogenation of alkenes/alkynes
Describe nucleophilic substitution of haloalkanes
Alkyl halides polarised at C-X bond = C electrophilic
Nu- replaces halide in C-X bond
