Chemistry Module 4.1 - page 89 Flashcards Preview

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What is the general formula?

The general formula is an algebraic formula that can describe any memeber of a family of compounds.

E.g. CnH2n+1OH (for all alcohols).


What is the empirical formula?

The simplest whole number ratio of atoms of each element in a compound.

E.g. Ethane, C2H6, would have an empirical formula of CH3.


What is the molecular formula?

The molecula formula is the actual number of atoms of each element in a molecule.


What is the structural formula?

Shows the arrangement of atoms carbon by carbon, with the attached hydrogens and functional groups.

E.g. Propane would have the structural formula of CH3CH2CH3.


What is the skeletal formula?

The skeletal formula shows the bonds of the carbon skeleton only, with any functional groups. The hydrogen and carbon atoms aren't shown. This is handy for drawing large complicated strcutures, like cyclic hydrocarbons.



What is the displayed formula?

The displayed formula shows how all the atoms are arranged, and all the bonds between them.



What is a homologous series?

A homologous series is a bunch of organic compounds that have the same functional group and general formula.


What is the suffix of an alkane? Give an example.

Suffix: -ane 

E.g. Propane, CH3CH2CH3


What is the suffix for a branched alkane? Give an example.

Suffix: alkyl- (-yl)

E.g. Methylpropane, CH3CH(CH3)CH3


What is the suffix for alkenes? Give an example.

Suffiix: -ene

E.g. Propene, CH3CH=CH2


What is the prefix for haloalkanes? Give an example.

Prefix: chloro-/bromo-/iodo-

E.g. Chlorothane, CH3CH2Cl


What is the suffix for alcohols? Give an example.

Suffix: -ol

E.g. Ethanol, CH3CH2OH


What is the suffix for aldehydes? Give an example.

Suffix: -al

E.g. Ethanal, CH3CHO


What is the suffix for ketones?

Suffix: -one

E.g. Propanon, CH3COCH3


What is the prefix and suffix of cycloalkanes?

Suffix and Prefix: cyclo-...-ane

E.g Cyclohexane, C6H12


What is the suffix for carboxylic acids?

Suffix: -oic acid

E.g. Ethanoic acid, CH3COOH


What is the prefix and suffix of esters?

Prefix and suffix: alkyl-...-anoate

E.g. Methyl propanoate, CH3CH2COOCH3


What do all organic compounds contain?

All organic compounds contain a carbon skeleton. This can be either aromatic or aliphatic.


What is an aromatic compound?

An aromatic compound is an organic compound which contains a benzene ring.


What is an aliphatic compound?

An aliphatic compound contain carbon and hydrogen joinmed together in straight chains, branched chains or non-aromatic rings.


What name would you give to an aliphatic compound which contains a (non-aromatic) ring?

If an aliphatic compound contains a (non-aromatic) ring, then it can be called alicyclic.


What is a saturated compound?

A saturated compound only contain carbon-carbon single bonds - like alkanes.


What is an unsaturated compound?

An unsaturated compound can have carbon-carbon double bonds, triple bonds or aromatic groups.


What is an alkyl group?

An alkyl group is a fragment of a molecule with general formula CnH2n+1.


GIve the method to name organic compounds.

1. Count the carbon atoms in the longest continuous chain -thid gives you the stem.

2. The main functional groupof the molecule usually tells you what homologous series the molecule is in, and so gives you the prefix or suffix.

3. Number the longest carbon chain so that the main functional group has the lowest possible number. If there's more than one longest chain, pick the one with the most side chains.

4. Any side chains or less important functional groups are added as prefixes ath the start of the name. Put them in alphabetical order, after the number of the carbon atom each is attached to.

5. If there's more than one identical side chain or functional group, use di- (2), tri- (3), tetra- (4) before that part of the name - but ignore this when working out the alphabetical order.


When are two molecules considered to be isomers of one another?

Two molecules are isomers of one another if they have the same molecular formula but the atoms are arranged differently.


What is a structural isomer?

A strucutural isomer is a molecule which has the same molecular formula but a different structural formula.


What are the three types of strucutural isomers.

The three types of structural isomers are:

Chain isomers, positional isomers and functional group isomers.


What is a chain isomer?

In a chain isomer, the carbon skeleton can be arranged differently, e.g. as a straight chain, or branched in different ways.

These isomers have similar chemical properties - bu their physical properties, like boiling point, will be different because of the change in shaoe of the molecule.


What is a positional isomer?

In a positional isomer, the skeleton and fucntional group could be the same, only the functional group attached to a different carbon atom.

These also have different physical properties, and the chemical properties might be different too.


What is a functional group isomer?

In a functional group isomer, the same atoms can bed arranged into different functional groups. 

These have very different physical and chemical properties.


What can atoms do around single C-C bonds?

Atoms can rotate as much as they want around single

C-C bonds. Therefore, a molecule may look like it has an isomer when it really doesn't.


What is an alkane?

Alkanes are saturated hydrocarbons.


What is the general formula for an alkane?

Alkanes have the general formula CnH2n+2


How many bonds does a carbon atom have with other atoms in an alkane?

Every carbon atom in an alkane has four single bonds with other atoms.



Are alkanes saturated or unsaturated hydrocarbons?

Alkanes are saturated - all the carbon-carbon bonds are single bonds.


Give the general formula of a cycloalkane.

Cn+2n is the general formula of cycloalkanes.


Explain why alkane molecules are tetrahedral around each carbon.

In an alkane molecule, each carbon atom has four pairs of bonding electrons around it. They all repel each other equally. So the molecule forms a tetrahedral shape around each carbon. Each bond angle is 109.5º.


Explain why the boiling point of an alkane depends on its size and shape.

1. Alkanes have covalent bonds inside the molecules. Between the molecules, there are induced dipole-dipole interactions which hold them together.

2. The longer the carbon chain, the stronger the induced dipole-dipole interactions. This is because there's more surface contact and more electrons to interact.

3. As the molecules get longer, it takes more energy to overcome the induced dipole-dipole interactions, and the  boiling point rises.

4. A branched chain alkane has a lower boiling point than its straight chain isomer. Branched chain alkanes can't pack closely together and they have smaller molecular surface areas - so the induced dipole-dipole interactions are reduced.


Detail the reaction between alkanes and oxygen (combustion).

1. If you burn (oxidise) alkanes with oxygen, you get carbon dioxide and water - it's a combustion reaction.

2. Combustion reactions happen between gases, so liquid alkanes have to be vaporised first. Smaller alkanes turn into gases more easily (they're more volatile), so they'll burn more easily too.

3. Larger alkanes release more energy per mole because they have more bonds to react.

4. Because they release so much energy when they burn, alkanes make excellent fuels.