Synthesis Flashcards
What happens when an organic reaction takes place?
Bonds in the reactant molecules are broken and bonds in the product molecules are made.
What is the process of bond breaking know as?
Bond fission
What are the types of bond fission?
Homolytic and hetrolytic
What does homolytic fission result in?
The formation of two neutral radicals
When does homolytic fission occur?
When each atom retains one electron from the sigma (σ) covalent bond and the bond breaks evenly.
Which type of fission usually occurs when non-polar covalent bonds are broken?
Homolytic fission
What do reactions involving Homolytic fission tend to result in?
(Relate it to organic synthesis)
The formation of very complex mixtures of products, making them unsuitable for organic synthesis.
What does Heterolytic fission result in?
The formation of two oppositely charged ions.
When does Heterolytic fission occur?
When one atom retains both electrons from the sigma (σ) covalent bond and the bond breaks unevenly.
What normally occurs when polar covalent bonds are broken?
Heterolytic fission
Which type of fission is better suited to for organic synthesis?
Heterolytic fission as it tends to result un far fewer products
What does a single-headed arrow indicate?
The movement of a single electron.
What does a double headed arrow indicate?
The movement of an electron pair.
What shows the source of the electron(s) when using curly arrow notation?
The tail of the arrow
What indicates the destination of the electron(s) when using curly arrow notation?
The head of the arrow
What indicates Homolytic fission?
(Curly arrow notation)
Two single headed arrows starting at the middle of a covalent bond
What indicates Heterolytic bond fission is occurring? (Curly arrow notation)
A double headed arrow starting at the middle of a covalent bond
What does an arrow drawn with the head pointing to the space between two atoms indicate?
(Curly arrow notation)
That a covalent bond will be formed between those two atoms
What are the 2 attacking groups involving Heterolytic bond fission classified as?
Nucleophiles and Electrophiles
What are Nucleophiles?
Negatively charged ions or neutral molecules that are electron rich that are attracted towards atoms bearing a partial or full positive charge and capable of donating an electron pair to form a new covalent bond.
What are some examples of molecules that are electron rich (Nucleophiles)?
Cl- , Br-, OH-, CN-, NH(3) and H(2)O
What are Electrophiles?
Positively charged ions or electron deficient neutral molecules that are attracted towards atom bearing a partial or full negative charge and capable of accepting an electron pair to form a new covalent bond.
What are some examples of neutral molecules that are electron deficient?
(Electrophiles)
H+, NO(2)+, SO(3)
When are alcohols substituted alkanes?
When on or more of the hydrogen atoms of the alkane is replaced with a hydroxyl functional group ( - OH)
What functional group is -COOH ?
Carboxyl group -> in carboxylic acids
What compounds would have a C=O functional group?
What is it called?
Aldehydes and Ketones.
Carbonyl functional group.
What are Haloalkanes?
(Alkyl halides) are substitutes alkanes in which one or more of the hydrogen atoms is replaced with a halogen atom.
How many halogen atoms do monohaloalkanes contain?
One
How can you determine if a monohaloalkane is primary, secondary or tertiary?
Depending on the number of alkyl groups attached to the carbon atom containing the halogen atom.
Monohaloalkanes take part in ___________ reactions using a strong base, such as ________ or _________to form alkanes
Elimination
Potassium or sodium hydroxide in ethanol
What do monohaloalkanes produce when they take part in nucleophilic substitution reactions with aqueous alkalis?
Alcohols
What do monohaloalkanes produce when they take part in nucleopjilic substitution reactions with alcoholic alkoxides?
Ethers
What do monohaloalkanes produce when they take part in nucleopjilic substitution reactions with ethanolic cyanide?
Nitriles (chain length increased by one carbon atom) that can be hydrolysed to carboxylic acids
What is SN1?
A nucleophilic substitution reaction with once species in the rate determining step and occurs in a minimum of two steps via trigonal planar carbocation intermediate.
What is SN2?
A nucleophilic substitution reaction with two species in the same rate determining step and occurs in a single step via a single five-centred, trigonal bipyramidal transition state.
Which are the two mechanisms monohaloalkanes can take part in nucleophilic substitution?
SN1 and SN2
What are the three ways alcohols can be prepared from?
- haloalkanes by substitution
- alkanes by acid-catalysed hydration (addition)
- aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride
