Hydroxy Compounds Flashcards
What are hydroxy compounds?
Organic compounds that contain the hydroxyl (-OH) functional group
What are the two types of hydroxy compounds?
- Alcohols (R-OH)
- Phenols (Ar-OH)
What are monohydric alcohols?
Alcohols that contain one -OH group
What are polyhydric alcohols?
Alcohols that contain more than one -OH group
What is the general formula of acyclic monohydric alcohol?
CnH2n+1OH
With comparable Mr, are boiling points of alcohols or alkanes higher and why?
Boiling points of alcohols are higher because more energy is required to overcome the stronger hydrogen bonds between the alcohol molecules than the weak id-id interactions between alkane molecules
What happens to the boiling point of alcohol as the number of C atoms increases?
As the number of C atom increases, the number of electrons in the molecule increases, more energy is required to overcome the stronger id-id between alcohol molecules, thus boiling point increases
For alcohols with comparable Mr, do branched or straight chain alcohol have a higher boiling point?
Straight chain has a higher boiling point because the surface area of the molecules is larger compared to more spherical, branched molecule. Thus more energy is required to overcome the more extensive id-id in straight chain than branched isomer
Are alcohols soluble in water and why?
Alcohols are soluble in water due to the presence of -OH group, which enable them to form hydrogen bonds with water molecules
As the number of carbon atom increases, what happens to the solubility of alcohol molecules?
As the number of carbon atom increases, the longer non-polar hydrocarbon chain hinders the formation of hydrogen bonds between the alcohol molecules and water molecules
Are alcohols soluble in organic solvents?
Yes
What are the methods to prepare alcohol?
- Electrophilic addition of steam to alkenes (industrial preparation)
- Electrophilic addition of conc. H2SO4 to alkenes, followed by heating with water (lab preparation)
- Nucleophilic substitution of OH- by alkyl halides
- Reduction of aldehydes, ketones, carboxylic acids and esters
- Fermentation of sugars/carbohydrates
What are the reagents and conditions for electrophilic addition of steam to alkenes to prepare alcohol?
steam, high temperature and pressure, H3PO4 catalyst
What is the reagents and conditions for electrophilic addition of conc. H2SO4 to alkenes to prepare alcohol?
cold conc. H2SO4, followed by heating with water
What is the reagents and conditions for nucleophilic addition of OH- on alkyl halides to prepare alcohols?
NaOH (aq) or KOH (aq), heat under reflux
What are the reagents and conditions for the reduction of esters to prepare alcohols?
LiAlH4 in dry ether
What are the reagents and conditions for the reduction of carboxylic acids to prepare alcohols?
LiAlH4 in dry ether
What are the reagents and conditions for the reduction of aldehydes to prepare alcohols?
- LiAlH4 in dry ether
- NaBH4
- H2, Ni catalyst, heat
What are the reagents and conditions for the reduction of ketones to prepare alcohols?
- LiAlH4 in dry ether
- NaBH4
- H2, Ni catalyst, heat
What is the equation of the reduction of aldehydes to prepare alcohols?
RCOH + 2[H] → RCH2OH (primary alcohol)
What is the equation of the reduction of ketones to prepare alcohols?
RCOR’ + 2[H] → RCR’HOH (secondary alcohol)
What is the equation of the reduction of carboxylic acids to prepare alcohols?
RCOOH + 4[H] → RCH2OH + H2O (primary alcohol)
What is the equation of reduction of esters to prepare alcohols?
RCOOR’ + 4[H] → RCH2OH + R’-OH (primary alcohols)
What is the equation for the fermentation of sugar/carbohydrates?
C6H12O6 -(yeast)→ 2CH3CH2OH + 2CO2
What are the reactions of alcohols?
- Combustion
- Elimination reaction
- Nucleophilic substitution of R-OH by -X
- Acid-metal reaction
- Condensation
- Oxidation
What flame do alcohols combust in?
Clean, hot flame
What types of elimination can alcohols undergo?
- Intermolecular dehydration of alcohols to form alkenes
- Intramolecular dehydration of alcohols to form ether
What are the reagents and conditions for the intramolecular dehydration of alcohols to form alkenes?
- Al2O3, heat
- excess conc. H2SO4, heat
What are the reagents and conditions for the intermolecular dehydration of alcohols to form ether?
conc. H2SO4, excess alcohol, heat
What are the types of nucleophilic substitution of R-OH by -X alcohols can undergo?
- Using HX (dry gas or conc. acid)
- Using dry PCl5
- Using PX3
- Using SOCl2
What are the reagents and conditions for the nucleophilic substitution of R-OH by -X using HX?
- HX (g), heat
- conc. HCl, ZnCl2 catalyst, heat under reflux
What is the equation for the nucleophilic substitution of R-OH by -X using HX?
R-OH + HX → R-X + H2O
How can HCl(g) be prepared as a reagent for nucleophilic sub with alcohol?
HCl(g) can be prepared in situ using KCl (s) + conc. H2SO4
How can HBr(g) be prepared as a reagent for nucleophilic sub with alcohol?
HBr(g) can be prepared in situ using KBr (s) + conc. H2SO4
How can HI (g) be prepared as a reagent for nucleophilic sub with alcohol?
KI (s) + conc. H3PO4
What is the order of reactivity of HX (most reactive to least reactive)?
HI > HBr > HCl
The bond energy increases from HI to HCl because the size of halogen atom decreases from I to Cl, and the valence orbitals become less diffused. This results in more effective overlap of orbitals between the small H atom and the larger halogen atom and thus more energy is required to break the stronger H-X bond
What are the reagents and conditions for the nucleophilic substitution of R-OH by -X using PX3?
PX3, room temp
What is the equation for the nucleophilic substitution of R-OH by -X using PX3?
3R-OH + PX3 → 3R-X + H3PO3
How is PBr3 prepared?
In situ by heating P4 and Br2