C11-. Organic Chemistry I Flashcards
What is a functional group defined as?
An atom/group of atoms responsible for the typical chemical properties/reactions of a molecule.
What is a homologous series?
A series of molecules with the same functional group but different numbers -CH2 groups. These all have a general formula.
What is the functional group of an alkene?
C=C with double bond
What is the functional group of a halogenoalkane?
R-X where X could be any halogen
What is the functional group of an alcohol?
-C-OH
What is the functional group of an aldehyde?
-COH with C=O
What is the functional group of a carboxylic acid?
-COOH with C=O
What is the functional group of a ketone?
C=O
What is the functional group of an ester?
-COO with O=C and C-O
Describe the naming convention for organic compounds, set by IUPAC.
- Prefixes - position and identity of side-chain substituents
- Stem: no. of carbon atoms in longest chain
- Suffix: functional group
How do we number functional group and side chains on a main carbon chain?
The functional group should be designated the lowest number possible.
When multiple substituent groups are present, how are they ordered?
Alphabetically, i.e. ethyl comes before methyl. This does not include prefixes like di-, tri-, tetra-.
Define empirical formula.
The simplest whole number ratio of atoms of each element in a compound.
Define structural formula.
Uses the smallest amount of detail necessary to show the arrangement of atoms in a molecule.
Define displayed formula.
Shows the relative positioning of all atoms in an molecule, and the bonding present between them.
Define skeletal formula.
A simplified organic formula, where hydrogen and carbon labels, and bonds to hydrogens atoms, are removed, leaving a carbon skeleton and functional groups.
What is structural isomerism?
When two or more molecules have the same molecular formula, yet have different structural formulae.
Define positional isomerism, and give examples of this with the context of C6H12.
- This occurs when the functional group occupies different positions along the chain.
- So this could be exemplified by C6H12, which could represent hex-1-ene, hex-2-ene, or even cyclohexane.
What is functional group isomerism?
This is when the function groups of organic molecules are different for the same molecular formula.
What is chain isomerism?
This occurs where the chain attached to the functional group changes in some way for a given molecular formula, such as hex-1-energy and 4-methylpent-1-ene.
Why are alkanes generally quite unreactive?
- Everything is covalently bonded. These bonds are not readily broken.
- Alkanes are non-polar molecules. This is because C-C bonds and C-H bonds are both considered non polar.
What are the products of the complete combustion of an alkane?
Carbon dioxide and water.
Give the causes and products of incomplete combustion of alkanes.
- If an insufficient oxygen supply is available, alkanes incompletely combust.
- This results in the production of carbon monoxide and soot.
What are the three types of species that can attack a molecule?
- Electrophile
- Nucleophile
- Free radical
What is a reaction mechanism?
This provides information about how a reaction takes place, i.e. what actually happens and the attacking species.
Define electrophile.
An electron pair acceptor. This means it is attracted to an electron rich centre, so it accepts a pair of electrons to form a new bond.
Define nucleophile.
An electron pair donor. This means it is attracted to an electron deficient centre, so it donates a pair of electrons to form a new bond.
Define free radical.
An atom/group of atoms with a single unpaired electron. These are highly reactive for this reason.
In what two ways can covalent bonds be broken?
- Homolytic fission
- Heterolytic fission
What is homolytic fission?
A covalent bond is split such that each resulting atom gains one of the electrons from the bonded pair. This results in the formation of 2 free radicals.
What is heterolytic fission?
A covalent bond is split such that one atom receives both electrons from a pair, and the other receives none. One positive and one negative atom are formed.
What are the differences in…
- speed of reaction
- reaction conditions
… between alkanes + halogens and alkenes + halogens?
- Speed of reaction is greatly reduced for alkanes (this is why organic compound + bromine water is still a good qualitative test for alkenes)
- Alkanes + halogens requires the presence of sufficient UV light
Why is UV light required during the reaction between an alkane and a halogen?
The UV light provides the initial energy required to enable homolytic fission to take place.
What three types of organic reaction mechanism do we need to be familiar with?
- Addition
- Substitution
- Elimination
What occurs during the initiation stage of the halogenation of an alkene?
The covalent bond within the halogen molecule undergoes homolytic fission in the presence of UV to form 2 halogen radicals.
What occurs during the propagation stage of the halogenation of an alkene?
The reaction propagates through a two-step chain reaction.
1. A halogen radical reacts with a C-H bond in methane to form a methyl radical and HBr.
2. This methyl radical reacts with a halogen molecule to form the halogenated product and a halogen radical.
What occurs during the termination stage of the halogenation of an alkene?
Two radicals collide, forming a stable molecule with all electrons paired. Any combination of radicals could react so there are a number of possible termination steps.
Name 2 limitations of radical substitution in organic synthesis.
- Further substitution - this can occur until all hydrogen atoms in a given organic compound have been substituted.
- Substitution can occur anywhere along the chain, giving rise to the formation of unwanted isomers.
