1. Introduction Flashcards
What is organic chemistry?
The study of carbon containing compounds, both natural and synthetic
(apart from carbon monoxide and carbon dioxide)
How many covalent bonds is carbon able to form with carbon atoms or non-metals?
4
Why are there so many carbon compounds?
Carbon has the ability to form four covalent bonds with other carbon atoms or non-metals
Why are carbon forms relatively stable compounds?
The C-C bonds are strong and therefore difficult to break
What can carbon compounds be represented using?
- empirical formula
- molecular formula
- general formula
- structural formula
- displayed formula
- skeletal formula
What is an empirical formula?
The simplest ratio of atoms of each element in a compound - may require cancelling numbers down
What is the empirical formula for any simple alkene?
CH2
What is a general formula?
An algebraic formula that can be used to describe any member of a family of compounds
General formula for alkanes?
CnH2n+2
General formula for alkenes?
CnH2n
General formula for alcohols?
CnH2n+1OH
What is a molecular formula?
A formula that gives the total number of atoms of each element in each molecule of a substance
What is a structural formula of an organic compound?
Shows the atoms carbon by carbon, with the attached hydrogens and functional groups
What is the structural formula of propene?
CH3CHCH2
What is the structural formula of chloroethane?
CH3CH2Cl
What is a displayed formula?
Shows how all of the atoms in a compound are arranged and show all of the bonds between them
What is a skeletal formula of an organic compound?
Shows the bonds of the carbon skeleton with only functional groups displayed
Which atoms are never drawn in a skeletal compound?
Carbon and hydrogen
What features of molecules are included when naming them?
- the size and shape of the carbon skeleton
- the presence of functional groups
- the position of functional groups
Why is carbon so important?
- forms long chains and structures
- forms single, double and triple covalent bonds
- forms basis of most organic compounds
What does the carbon skeleton provide the name for?
The ‘backbone’ of the molecule around the rest is constructed
If a molecule’s carbon skeleton consists of 1 carbon atom, what will its name include?
Meth-
If a molecule’s carbon skeleton consists of 2 carbon atoms, what will its name include?
Eth-
If a molecule’s carbon skeleton consists of 3 carbon atoms, what will its name include?
Prop-
If a molecule’s carbon skeleton consists of 4 carbon atoms, what will its name include?
But-
If a molecule’s carbon skeleton consists of 5 carbon atoms, what will its name include?
Pent-
If a molecule’s carbon skeleton consists of 6 carbon atoms, what will its name include?
Hex-
What are main chains named after?
The maximum number of carbon atoms bonded in a ‘straight chain’
What are branched chains named after?
The number of carbons they contain
Where does the name of branched chains go when naming a molecule?
At the beginning; they form a prefix to which -yl is added
What is added to the end of names of branched chains?
-yl
How are ring structures named?
- cycloalkanes
* cycloalkenes
How can cycloalkenes also be known?
Arenes
What compound are arenes based on?
Benzene
What are arenes?
Aromatic compounds
What is a functional group?
The part of the molecule where reactions take place
What does the functional group of a compound identify?
Its homologous series - and is therefore used to name it
What is a homologous series?
A group of compounds that contain the same functional group
What is the functional group of alkenes?
C=C
What is the functional group of alcohols?
-OH
What is the functional group of carboxylic acids?
-COOH
In a homologous series, how will each member differ from the other?
CH2
How does being in the same homologous series affect the properties of compounds?
- physical - length affects physical properties
* chemical - properties are the same
What do physical properties of organic compounds differ with?
- size
* degree of branching
What are examples of physical properties of organic compounds?
Melting and boiling point
How will increased chain length affect the melting and boiling point of molecules?
- increase melting and boiling points
* because strength of intermolecular force between molecules increases
How will increased branching affect the melting and boiling point of molecules?
- decrease melting and boiling points
* because molecules cannot pack together as easily (weaker intermolecular forces between molecules)
If there is no functional group, what will the name of the molecule end with?
‘ane’
What is the functional group in haloalkanes?
A halogen
What is the functional group in aldehydes?
O=C-H
What is the functional group in ketones?
O=C-
What is the functional group in nitriles?
-C≡N
What is the functional group in amines?
C - NH2
What is the prefix/suffix for alkenes?
suffix: -ene
What is the prefix/suffix for alchols?
suffix (usual use): -ol
prefix: hydroxy-
What is the prefix/suffix for haloalkanes?
prefix: chloro-, bromo-, iodo-
What is the prefix/suffix for aldehydes?
suffix: -al
What is the prefix/suffix for ketones?
suffix (usual use): -one
prefix: oxo-
What is the prefix/suffix for carboxylic acids?
suffix: -oic acid
What is the prefix/suffix for nitriles?
suffix: -nitrile
What is the prefix/suffix for amines?
suffix (usual use): -amine
prefix: amino-
If there is more than 1 functional group or side chain, what should be used before the corresponding part of the name?
- di-
- tri-
- tetra-
What are the four steps for naming organic compounds?
- Identify the principle functional group
- select the longest continuous carbon chain that contains the functional group
- number carbon atoms from end that gives lowest number to principle functional group
- identify additional functional groups and side chains
Are alkenes saturated or unsaturated?
Unsaturated
Are alkanes saturated or unsaturated?
Saturated
What are haloalkanes?
Alkanes in which one or more of the hydrogen atoms have been replaced by a halogen atom
In haloalkanes, when does the position of the halogen need to be identified?
When the carbon chain is longer than two carbons
When naming haloalkanes, and there are more than one halogen, how are the prefixes listed?
In alphabetical order
When do branched chains exist?
When one or more hydrogen atoms in the chain have been replaced by a side chain
In structural formulae, how are side chains represented?
In brackets - after the carbon it is attached to
apart from when chain is on 1st carbon - in this case it is before the carbon its attached to
If a side chain has 1 carbon atom, what is its prefix?
Methyl-
If a side chain has 2 carbon atoms, what is its prefix?
Ethyl-
If a side chain has 3 carbon atoms, what is its prefix?
Propyl-
If a side chain has 4 carbon atoms, what is its prefix?
Butyl-
How is it indicated that a compound is a ring structure instead of a straight chain?
By adding the prefix ‘cyclo-‘
Do cyclic structures follow the general formula of the homologous series?
No
What is the name for the molecule with the structural formula CH₃CH₂CH(CH₃)CH₂CHFCH₃?
2-Fluro, 4-Methylhexane
What are isomers?
Molecules that have the same molecular formula but a different arrangement of atoms
What is a structural isomer?
Molecules with the same molecular formula but a different structural formula
What could a different arrangement of covalent bonds result from?
- different arrangement of the carbon skeleton (chain isomerism)
- functional group being in different positions (position isomerism)
- a different functional group (functional group isomerism)
What is position isomerism?
Same carbon skeleton but functional groups are in different positions along the chain
What do reaction mechanisms allow for?
Predictions of what might happen to an organic molecule with a particular reagent
What is a radical?
An atom or molecule with an unpaired electron
Why are radicals very reactive?
They have an unpaired electron
How is an unpaired electron on a radical represented?
By a dot
What are radicals caused by?
Homolytic fission
What is homolytic fission?
The breaking of a covalent bond in such a way that one electron goes to each atom
What can radicals react with?
Molecules and other radicals
What are ‘curly arrows’ used to show?
The movement of electrons - and hence explain what’s happening in a reaction
What does a curly arrow with half a head represent?
The movement of a single electron
What does a curly arrow with a full head represent?
The movement of an electron pair
How do curly arrows show the direction of movement of electrons?
The tail shows where the electrons come from; the head shows where they end up
How is the formation of a covalent bond shown using a curly arrow?
The arrow starts from a lone electron pair or from another covalent bond
How is the breaking of a covalent bond shown using a curly arrow?
The arrow starts from the bond
Which molecules show position isomerism?
- alkenes with 4 or more carbon atoms
- haloalkanes with 3 or more carbon atoms
- alcohols with 3 or more carbon atoms
Do alkanes show position isomerism?
No
What are the two position isomers of C4H8?
- but-1-ene
* but-2-ene
What are two position isomers of C3H7Cl?
- 1 - chloropropane
* 2-chloropropane
What are two position isomers of C3H7OH?
- propan-1-ol
* propan-2-ol
What is chain isomerism?
Same functional group but different arrangement of the carbon skeleton
Which molecules show chain isomerism?
All molecules containing four or more carbon atoms
What are two chain isomers of C4H8?
- but-1-ene
* 2-methylprop-1-ene
What are two chain isomers of C4H9Cl?
- 1-chlorobutane
* 2-methyl, 1-chloropropane
What are two chain isomers of C3H7COOH?
- butanoic acid
* 2-methyl propanoic acid
What is functional group isomerism?
Isomers that have the same molecular formula but contain different functional groups
What molecules show functional group isomerism?
- alkenes and cycloalkanes
- carbonyls (aldehydes and ketones), alkenols and cycloalcohols
- 1°, 2° and 3° amines and amides
- esters and carboxylic acid
What do alkenes show functional group isomerism with?
Cycloalkanes
What do carbonyls (aldehydes and ketones) show functional group isomerism with?
Alkenols and cycloalcohols
What do esters show functional group isomerism with?
Carboxylic acid
What are two functional group isomers of C3H6O?
- propan-2-one
* propanal
What is stereoisomerism?
When two compounds have the same structural formula but differ in the arrangement of bonds in the space
What are stereoisomers?
Compounds with the same structural formula but with a different arrangement of atoms in the space
What type of isomerism is E-Z?
Stereoisomerism
When does E-Z isomerism occur?
In molecules containing a double C=C bond, when both carbon atoms forming the double bond are attached to different groups
What is E-Z isomerism a result of?
Restricted rotation about the planar carbon-carbon double bond
When is it an E isomer?
When two higher priority groups are on opposite sides of the double bond
When is it a Z isomer?
When two higher priority groups are on the same side of the double bond
What are the rules for determining priority known as?
CIP rules
Which atoms are given higher priority when classifying E-Z isomers?
Those with the highest atomic numbers
How are the highest priority groups decided?
- group with highest atomic number is given highest priority
* group with lowest atomic number given lowest priority
What happens when determining priority if there is a double bond present in any of the groups?
The atom bonded to the double bond is counted twice
What happens when determining priority and it is the same atom on both sides?
Look at each atom until a difference is found - the atomic number of those atoms needs to be used to determine priority
What is the isotope of hydrogen with a relative atomic mass of 2?
Deuterium
Would hydrogen and deuterium have the same priority?
Yes - in terms of atomic number. In this case deuterium will have priority as it has a higher relative atomic mass
When there are two isotopes and they both have the same atomic number, which takes priority?
The one with the higher relative atomic mass
What is the relative atomic mass of deuterium?
2
Why can E/Z isomerism occur in di-substituted cycloalkanes?
Because the ring prevents rotation of the C-C bond
