Basic Organic Flashcards
What are halogenoalkanes?
An alkane where at least one hydrogen has been substituted by a halogen
What is a:
- Primary halogenoalkane
- Secondary halogenoalkane
- Tertiary halogenoalkane
- The halogen is bonded to a carbon bonded to 1/2/3 carbons
What are some properties of halogenoalkanes?
- As chain length increases, the strength of the induced dipole dipole forces increases and mp increases (not dipole dipole)
- Halogenoalkanes are polar molecules due to the differing electronegativities between the carbon and the halogen
- C-H bonds are non-polar
What increases the strength of idd?
- Number of electrons
- Points of surface contact
Why are halogenoalkanes only slightly soluble at best despite being polar molecules?
- The strength of the idd and the dd are not stronger than the hydrogen bonds which have to be broken to make way for these interactions
What is a nucleophile?
An electron pair donor
What is a reagent?
A physical substance added to a system
What reagents are used for nucleophilic substitution of halogenoalkanes to produce alcohols?
NaOH, KOH Dissolved in water to release ions (aq)
Why can halogenoalkanes take part in nucleophilic substitution?
The halogen is more electronegative than the carbon causing a polar bond which can act as an electrophile for a nucleophile.
What reagents are required for nucleophilic substitution of halogenoalkanes to produce alkanenitriles?
NaCN, KCN dissolved in liquid ethanol.
This is because if NaCN dissolves in water, it could produce OH instead of CN and forming an alcohol rather than alkanenitriles.
Which halogenoalkane undergoes nucleophilic substitution fastest?
C-I lowest bond enthalpy, lower activation energy, increased fsc
C-F highest electronegativity differences, right orientation, increased fsc
Determined by bond enthalpy
How to measure rate of nucleophilic substitutions in halogenoalkanes?
To measure the reactivity of halogenoalkanes, we first dissolve the halogenoalkane in
ethanol. Then, we add
water and AgNO3 and measure how long it takes a precipitate to form.
What is a free radical?
A reactive species with an unpaired electron
How to produce a halogenoalkane?
Addition reaction
Free radical substitution
What does heterolytic fission result in?
Ions
What does homolytic fission result in?
What conditions required?
Free radicals
Heat
Temp > 450
UV Light (more energy)
Why does the carbon-halogen bond enthalpy decrease down the group?
What do uncontrollable side reactions do/ multiple substitution?
How to limit the effects of this?
- Increased time taken to produce desired products
- Decrease percentage yield
- Same atom economy
- Use excess reactant (alkane) rather than excess halogen
What is a CFC?
What are they used for?
Chlorofluorocarbon
Refrigerants
Aerosol
What is a homologous series and what are some features of it?
- Families of organic compounds with the same functional group and same general formula
- Differ by CH2
- Same chemical properties
- Gradual change in physical properties
What are structural isomers?
What are the types?
Compounds with the same molecular formula but different structural formula
- Chain isomers
- Position isomers
- Functional group isomerism (e.g aldehydes and ketones)
What does a double headed curly arrow show?
Movement of a pair of electrons
Why does the melting point of alkanes increase as chain length increases?
There are more electrons and points of surface contact which increases the strength of induced dipole dipole interactions, meaning more energy is required to overcome the bonds between molecules.
Why do alkanes how low reactivity?
- High bond enthalpies of C-C bond
- Low polarity of C-H (not attractive to nucleophiles/electrophiles)
What is cracking?
Conversion of long-chain hydrocarbons to short-chain hydrocarbons (alkanes, alkenes and hydrogen)
Why are pi bonds so susceptible to electrophilic attack?
They are exposed and have high electron density
What is stereoisomerism?
When compounds have the same structural formula but different arrangements of atoms/groups in space
When does E-Z stereoisomerism arise?
- Restricted rotation around the C - C double bond
- There are different groups attached to the carbon atoms
- C-C single bonds can rotate
What is cis- trans isomerism?
A type of stereoisomerism where two of the groups are the same
How does E-Z isomerism have an effect on physical properties e.g boiling point?
If a molecule is cis, it can be polar meaning that it also has pdd and idd. If a molecule is trans, the polarity could cancel out meaning it only has idd forces.
Addition Reactions of Alkenes:
+ Hydrogen
Reagents:
Catalyst:
Type of Reaction:
- Hydrogen
- Nickel
- Addition/ Reduction
Electrophilic Addition Reactions of Alkenes:
+ Halogens
Reagents:
Type of Fission:
Product:
- Halogen (no UV- not homolytic)
- Heterolytic
- Dihaloalkane
Electrophilic Addition Reactions of Alkenes:
+
