Characteristic Organic Reactions (Cambridge (CIE) A Level Chemistry): Flashcards
Exam code: 9701
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Define addition reaction.
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Define addition reaction.
An addition reaction is an organic reaction in which two or more molecules combine to give a single product with no other products formed.
What is the difference between a substitution reaction and an elimination reaction?
A substitution reaction replaces one atom or group with another, whereas an elimination reaction removes a small molecule (such as H2O or HCl) from an organic molecule to form a new bond.
True or False?
In organic chemistry, oxidation involves the addition of oxygen or removal of hydrogen.
True.
In organic chemistry, oxidation is typically the addition of oxygen or removal of hydrogen atoms. The symbol [O] represents one oxygen atom from an oxidising agent.
Define condensation reaction.
A condensation reaction is a reaction in which two organic molecules join together and in the process eliminate a small molecule such as H2O or HCl.
Saturated hydrocarbons contain .......... bonds only, while unsaturated hydrocarbons contain carbon-carbon .......... or .......... bonds.
Saturated hydrocarbons contain single bonds only, while unsaturated hydrocarbons contain carbon-carbon double or triple bonds.
What is a hydrolysis reaction?
A hydrolysis reaction is one in which a compound is broken down by water (or by dilute acids or alkalis).
True or False?
In organic chemistry, reduction involves the addition of hydrogen or removal of oxygen.
True.
In organic chemistry, reduction is typically the addition of hydrogen atoms or removal of oxygen. The symbol [H] represents one hydrogen atom from a reducing agent.
A .......... reaction replaces an atom or group of atoms with another atom or group, whereas a .......... reaction combines two molecules into one with no other products.
A substitution reaction replaces an atom or group of atoms with another atom or group, whereas an addition reaction combines two molecules into one with no other products.
In organic redox equations, what do the symbols [O] and [H] represent?
[O] represents one oxygen atom from an oxidising agent and [H] represents one hydrogen atom from a reducing agent. They are used to balance organic redox equations simply.
Define curly arrow (organic mechanisms).
A curly arrow in an organic mechanism represents the movement of an electron pair, drawn from the source (a bond or lone pair) to the species that accepts the electrons.
What are the three steps of a free-radical substitution reaction, in order?
The three steps are initiation, propagation and termination.
True or False?
In the initiation step of free-radical substitution, UV light breaks the Cl–Cl bond by homolytic fission.
True.
UV light provides energy to break the Cl–Cl bond homolytically, giving each chlorine atom one electron and forming two chlorine radicals (Cl•).
Define electrophilic addition.
An electrophilic addition is a reaction in which an electrophile attacks an electron-rich region of a molecule and a small molecule adds across a double bond to give one product.
In free-radical substitution propagation, CH4 + Cl• → .......... + HCl. The alkyl radical then reacts with Cl2 to form .......... and regenerate Cl•.
In free-radical substitution propagation, CH4 + Cl• → •CH3 + HCl. The alkyl radical then reacts with Cl2 to form CH3Cl and regenerate Cl•.
What is nucleophilic substitution and what acts as the leaving group?
Nucleophilic substitution is a reaction in which an electron-rich nucleophile displaces a halogen atom from a halogenoalkane. The displaced halide ion (X-) is the leaving group.
True or False?
In the termination step of free-radical substitution, only one product is possible.
False.
Multiple products are possible in termination depending on which two radicals combine. For example, •CH3 + •CH3 → CH3CH3 is an undesirable by-product.
Define nucleophilic addition.
A nucleophilic addition is a reaction in which a nucleophile attacks an electron-deficient region of a molecule, followed by addition of a small molecule to give one product.
In a halogenoalkane, the C–X carbon is electron-deficient (..........) because the halogen is more .......... than carbon and pulls electrons towards itself.
In a halogenoalkane, the C–X carbon is electron-deficient (δ+) because the halogen is more electronegative than carbon and pulls electrons towards itself.
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