Organic Chemistry Pt 2 - Week 19 - 20 Flashcards
What directing effect does a negative charge cause?
Negative charge concentrates at ortho and para positions
What directing effect does a positive charge cause?
Positive charge concentrates at ortho and para positions
What are some examples of strongly activating ortho-para directors?
-NH2, , -NHR, -NR2, -OH, -NHR, -O2CR
What are some examples of weakly activating ortho-para directors?
-C6H5, -CH3, -CH(CH3)2, -R, -CH2CH3,
-F, -Cl, -BR, -I
What are some examples of weakly deactivating meta directors?
-CHO, -COR, -SO3H, -CO2H, -CO2R
What are some examples of strongly deactivating meta directors?
-CN, -NH(CH3)3 -NO2
What pushes lone pairs into the ring by resonance?
Ortho-para directors
What can pull electrons out of the ring by resonance?
Meta directors
What is oxidation?
Loss of hydrogen (electrons) and gain of oxygen
What is reduction?
Loss of oxygen and gain of hydrogen (electrons)
What are oxidising agents?
Reagents that oxidise C atoms by adding O atoms
Have lots of oxygen and an atom at a high oxidation state.
What are reducing agents?
Reagents that reduce C atoms by adding H atoms
Why is knowing the pKa of an organic molecule usefull?
It is useful for predicting state of functional groups in a reaction mixture
pH > pKa basic form pH < pKa acidic form
Helps predict reactivity for unknown or unfamiliar mechanisms
What is the general formula of alcohols?
CnH2n+1OH
What are the physical properties of the state, density and intermolecular forces of alcohols?
State - usually liquids or solids at RT
Density - less dense than water
Intermolecular forces - Hydrogen bonding,
Dipole-Dipole, Van der Waal
Explain the boiling point of alcohols?
- Higher than hydrocarbons and alkyl halides
of similar chain length - Increases with chain length
- Affected by branching
Explain the miscibility of alcohols:
- Alcohols are generally miscible with organic
solvents - Short alcohols ~ 3-4 carbon atoms are fully
miscible in water - Dependent on branching
What and how are primary alcohols oxidised to?
Primary alcohol –> Distillation to aldehyde
Primary alcohol –> Reflux –> Carboxylic acid
H2SO4 CrO42-
Explain the oxidation of secondary alcohols:
secondary alcohol –> reflux —-> ketone
H2SO4 CrO42-
Explain the oxidation of tertiary alcohols:
tertiary alcohol –> Reflux —> NO REACTION
What are the conditions for reflux?
H2SO4
CrO42- / Cr2O72-
How are alkyl chlorides formed using SOCl2?
C2H5OH + SOCl2 —-> C2H5Cl + SO2 + HCl
How are alkyl bromides formed using PBr3?
3 C2H5OH + PBr3 —-> 3 C2H5Br + H3PO3
How are metal alkoxides formed?
- similar to reaction of reactive metals with
water
2M + 2 H2O –> 2 MOH + H2
What forms after the dehydration of alcohols?
Alcohols + heat –> (conc H2SO4 or H3PO4) and reflux –> alkenes
What occurs in the deprotonation of alcohols?
Acid - Base reaction to form an alkoxide
R-OH + B: - < —> R - O- + BH
What are the physical properties (state, miscibility, density and intermolecular forces) of aldehydes/ketones?
State - usually solid or liquid at RT
Miscibility - generally miscible with organic
solvents
- short chains miscible in water
- dependent on branching
Density - less dense that water
Intermolecular forces - Dipole-Dipole, Van der
Waal
Boiling point - Higher than hydrocarbons and
alkyl halides of similar chain length
- Increases with chain length
- Affected by branching
What is cyanohydrin formation?
Addition of HCN to a carbonyl
CH3COCH3 –> (KCN H2SO4) –>
CH3COHCCNCH3
What is cyclic hemiacetal formation?
- how sugars convert from linear to ring
conformation - Cyclic hemiacetals are stable and isolable
(capable of being isolated or disjointed)
What is imine formation?
How primary amines and ammonia react with carbonyls
CH3COCH3 + CH3-NH2 ——> CH3CN(CH3)CH3 + H2O
Why does alpha carbon deprotonate?
Alpha carbon has relatively acidic C-H bonds (pKa ~ 20) —> easy to deprotonate for an additional reactivity center
What conditions does deprotonation of alpha carbon occur?
Can deprotonate under both acidic (enol) and basic (enolate) conditions.
How does Grignard reagents form?
Formed when certain metals are added to alkyl halides
C4H9Br —-> (Mg metal) (Et2O or THF) –>
C4H9MgBr
What are the trends in the states of matter of acid chlorides and esters?
- Acids, acid chlorides, esters - usually liquids
at RT - Amides and anhydrides usually solids at RT
What are the trends in the density of acid chlorides and esters?
Esters are less dense than water
What are the trends in miscibility of acid chlorides and esters?
- Very few amides are soluble miscible in
water - Esters are soluble/miscible in water
- Shorter chain carboxylic acids are miscible in
water - Acid chlorides and anhydrides react in water
so are incompatible
What are the trends in boiling point of acid chlorides and esters?
- Trend depends on intermolecular forces
possible. - Increases with chain length
- Affected by branching
What intermolecular forces are present in acid chlorides and esters and anhydrides?
Dipole-dipole and Van der Waal forces
- can accept hydrogen bonds from a polar
protic solvent
What intermolecular forces are present in carboxylic acids and amides?
Hydrogen bonding, Dipole-dipole and Van der Wall forces
Which reagents work in the reduction of acid chlorides?
- LAH (excess) - H3O+
and
- NaBH4 (excess) - H30+
What happens when you add multiple equivalents of Grignard or Organolithium reagents to an ester?
= tertiary alcohol and R’ - OH forms
What happens when you add multiple equivalents of Grignard or Organolithium reagents to an acid chloride?
= a tertiary alcohol and HCl
What happens when you add multiple equivalents of Grignard or Organolithium reagents to an acid anhydride?
= a tertiary alcohol and a tertiary alcohol
What happens to organometallic /grinyard reagents in the presence of protic N-H or O-H bonds?
They act like a base and get protonated
What are the states of matter, miscibility and density of amines?
State - Usually liquids or solids at RT
Miscibility - Small amines (< 5-6 carbon atoms) are miscible with water
Density - Less dense than water
What intermolecular forces are present within amines?
Hydrogen bonding, Dipole-dipole, Van der Waal
What are the trends in boiling point of amines?
As chain length increases boiling point increases.
As the amide group becomes more branched boiling point decreases.
What are the trends in reactivity of amines?
- Amines are both nucleophilic and a weak
base - They will be protonated by acids
