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CHEMISTRY U1/2 > CHAPTER 8: ORGANIC CHEMISTRY > Flashcards

CHAPTER 8: ORGANIC CHEMISTRY Flashcards

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1
Q

what are hydrocarbons

A
  • hydrocarbons are organic molecules that are covalently bonded and only contain hydrogens and carbons.
  • they can contain single, double and triple bonds
  • hydrocarbons are NON-POLAR
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2
Q

physical properties of alkanes

A
  • alkanes are non-polar
  • insoluble in water
  • only dispersion forces between molecules
  • number of carbons and size of molecules increases within any homologous series, therefore strength of dispersion forces increases
  • melting and boiling points of alkane increases as number of carbons in the molecules increases
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3
Q

chemical properties of alkanes

A
  • alkanes are relatively unreactive, but they can be used as fuel
  • combustion reaction involves the burning of a compound with oxygen to produce water and carbon dioxide.
  • the burning of petrol in a car engine and the use of natural gas for cooking are examples of combustion reactions.
  • the general formula for combustion looks like this:
    hydrocarbon + O2 -> CO2+ H2O
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4
Q

different ways of representing alkanes

A
  • The condensed structural formula (also known as semi-structural formula)
    • shows how the atoms are connected, but without drawing the bonds
      eg. CH3CH3
  • Structural formulas are similar to valence structure- but lone pairs are left out!
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5
Q

naming hydrocarbons

A
  • We name hydrocarbons based on:
    • how many carbons are in the longest molecular chain.
    • the type of bonds that exist between carbon atoms (i.e. single, double, triple)
      number of carbon:
      1 = meth-
      2 = eth-
      3 = prop-
      4 = but-
      5 = pent-
      6 = hex-
      7 = hept-
      8 = oct-
      9 = non-
      10 = dec-
      type of bond
      single = -ane
      double = -ene
      triple = -yne
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6
Q

families of hydrocarbons - homologous series

A
  • in a homologous series, each member has one more –CH2 unit than the previous member.
  • members of a homologous series have similar structures and chemical/physical properties and same general formula.
  • examples of homologous series/families are:
    • Alkanes
    • Alkenes
    • Alkynes
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7
Q

what are alkanes

A
  • alkanes are saturated hydrocarbons that contain only single bonds and have a general formula CnH2n+2
    • alkanes always end with the suffix – ane.
    • alkanes are relatively unreactive, although they do undergo combustion reactions.
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8
Q

what are structural isomers

A
  • when two molecules have the same molecular formula but different molecular structures
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9
Q

what are alkyls

A
  • are side chains
  • named after the alkane derived from
  • have one less hydrogen than the alkane
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10
Q

nomenclatures

A
  • as molecules get bigger, the number of structural isomers increases
  • we need a systematic way to name each molecule so that it has a distinct name
  • this system developed by IUPAC (international union of pure and applied chemistry) is known as systematic nomenclature
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11
Q

steps for naming an alkane

A
  1. Identify the longest unbranched carbon chain.
  2. Number the carbon atoms in the chain from the end that will give the smallest numbers to branches
  3. Name the branching alkyl groups according to the alkane from which they are derived
  4. Place the number and position of each of the alkyl groups at the beginning of the compounds name.
  5. If there are two identical branches, use ‘di-’ as a prefix; for three use ‘tri-’.
  6. If there are alkyl side chains of different lengths on the molecule, list them in alphabetical order at the start of the name, with their numbers to indicate their respective positions.
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12
Q

physical properties of alkenes

A
  • alkenes are non-polar
  • insoluble in water
  • only dispersion forces between molecules
  • number of carbons and size of molecules increases within any homologous series, therefore the strength of dispersion forces increases
  • melting and boiling points of alkene increase as the number of carbons in the molecules increase
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13
Q

chemical properties of alkenes

A
  1. Combustion Reactions
    - Similar to Alkanes, Alkenes can be involved in combustion reactions,
    involving them burning with oxygen to produce water and carbon
    dioxide

E.g. Ethene + Oxygen → Carbon Dioxide + Water

  1. Addition reactions
    - The reason why alkenes are more reactive than alkanes
    - In addition reactions, the double bond is split to incorporate the other reactant
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14
Q

test for saturation

A
  • It is possible to use bromine solution to test for the saturation of organic molecules.
  • Bromine solution is usually brown, but it goes clear when it undergoes an addition reaction.
  • In the presence of alkanes it will not react and therefore stay brown.
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15
Q

what are polymers

A
  • polyethene is an example of a polymer
  • polymers are long molecules formed from the linking of many small molecules (called monomers)
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16
Q

what are alkenes

A
  • alkenes are unsaturated hydrocarbon molecules that contain at least 1 carbon-carbon double bond and have a general formula CnH2n.
  • alkenes always end with the suffix -ene.
  • alkenes are more reactive than alkanes
  • note: Alkenes are non-polar, hence do not dissolve in water
17
Q

naming alkenes

A
  1. Identify the longest unbranched carbon chain. The chain must include the double bond.
  2. Number the carbon atoms in the chain from the end that will give the smallest numbers to double-bonded.
  3. Name the branching alkyl groups
  4. Identify the position of the double bond by the number of the first carbon atom involved in the bond. Use the suffix ‘-ene’ to indicate the presence of a double bond, e.g. hex-2-ene.
  5. Place the number and position of each of the alkyl groups at the beginning of the compounds name in alphabetical order.
  6. If there are two identical branches, use ‘di-’ as a prefix; for three use ‘tri-’.
  7. If there are different alkyl side chains, list them in alphabetical order at the start of the name, with their numbers/positions (Remember triethyl comes before dimethyl! Do not line up ‘t’ and ‘d’. Always look at the alkyl.)
18
Q

what are functional groups

A
  • most organic compounds can be regarded as derivatives of hydrocarbons
  • in general, when one or more H atoms in a hydrocarbon is replaced by other atoms or groups of atoms (known as functional groups), a new homologous series is created
  • the organic molecules can form covalent bonds with other atoms/group of atoms
  • the functional group gives a molecule particular physical and chemical properties
19
Q

what are haloalkanes

A
  • derived from alkanes
  • at least one H in an alkane is replaced by a halogen atom
  • halogens have 7 valence electrons and will form a single covalent bond
  • new homologous series forms – haloalkanes
  • general formula CnH2n+1X, where X is F, Cl, Br or I
20
Q

uses of haloalkanes

A
  • Used widely in industry for
    • Flame retardants
    • Refrigerants
    • Propellants
    • Pesticides
    • Solvents
    • Pharmaceuticals
21
Q

physical properties of haloalkanes
effect of shape of the molecule

A
  • most haloalkanes are polar; some are non-polar
  • polarity depends on the shape of the molecule
  • solubility depends on the polarity of the molecule
    • non-polar = not soluble
    • more polar = more soluble
  • intermolecular forces
    • non-polar molecules = Only dispersion forces
    • polar molecules = Dispersion forces and dipole-dipole forces
22
Q

physical properties of haloalkanes
effect of the halogen (group 17) atom size

A

the larger the size of the halogen atom, the higher the boiling point of the haloalkane

23
Q

physical properties of haloalkanes
effect of carbon chain length

A

longer carbon chain length → less polar → less soluble in water

24
Q

chemical properties of haloalkanes

A

substitution reaction

  • significantly more reactive than alkenes
  • halogen is replaced with a hydroxide (-OH) functional group
25
Q

naming haloalkanes

A
  • Place the name of the specific halo functional group at the start of the parent alkane name
  • Use numbers to indicate the carbon to which halo functional group is attached
  • Number the C chain from the end that gives the smallest number to the halo group
  • List multiple halo groups in alphabetical order
  • Use prefixes ‘di-’, ‘tri-’ etc if multiple identical halo groups are present
  • WHEN NUMBERING THE CARBONS IN A HALOALKANE, THE NUMBERING SHOULD START FORM THE END NEAREST THE HALOGEN
26
Q

what are alcohols

A
  • this is a -OH group
  • known as a hydroxyl group
  • it replaces a H in the hydrocarbon
  • successive members in this homologous series differ by a -CH2- group
  • general formula is CnH2n+1OH
  • prefix = Normal (eth-, prop-, but- etc)
  • suffix (ending) = is always ‘-ol’
  • alcohols are polar, hence will dissolve in water
27
Q

physical properties of alcohols

A
  • all alcohols are liquids at room temperature
  • higher boiling points of alcohols are higher than the corresponding alkanes due to hydrogen bonding
  • increase in alcohol molecule size leads to increase in boiling point
  • solubility
    • decreases as the length of the carbon chain attached to –OH increases
    • a longer chain means that more of the molecule becomes non-polar
  • intermolecular forces
    • dispersion forces, dipole-dipole forces and hydrogen bonding
28
Q

chemical properties of alcohols

A
  • alcohol undergoes combustion reactions
    • Similar to alkanes and alkenes can be involved in combustion reactions, involving them burning with oxygen to produce water and carbon dioxide
29
Q

naming alcohols

A
  • remove the e from the end and add ‘-ol’
  • the numbers on the carbons are numbered from the end that is closest to the functional group.
    eg. butan-2-ol
30
Q

what are carboxylic acids

A
  • this is a -COOH group
  • known as a carboxyl group
  • it replaces 3 H in the hydrocarbon
  • general formula = RCOOH where R is an alkyl group (e.g. -$CH_{3}$ and - $C_{2}H_{5}$
  • successive members of the series differ by a –CH2 unit
  • prefix = Normal (eth-, prop-, but- etc)
  • suffix (ending) = is always ‘-oic acid’
  • carboxylic acids are polar, hence will dissolve in water
31
Q

uses of carboxylic acid

A
  • carboxylic acids are organic acids.
  • they are commonly found in nature, giving a sour taste to lemon juice and vinegar, or making an ant bite or a nettle prick sting
32
Q

physical properties of carboxylic acid

A
  • carboxylic acids have higher boiling points compared to alcohols of similar molecular size
    • Because of the hydrogen bonds that form between two carboxylic molecules
    • Known as a dimer
    • Increases dispersion forces between the dimers, resulting in a higher boiling point
  • carboxylic acids are more soluble than alcohols in water
    • because hydrogen bonding occurs between the carboxyl group of carboxylic acids and water molecules
  • solubility of carboxylic acids decrease as they increase in size
    • A longer carbon chain means more of the
      molecule is non-polar
33
Q

chemical properties of carboxylic acids

A
  • carboxylic acids undergo acid-base reactions
  • carboxylic acids react with water to produce a carboxylate ion, with the functional group R-COO-
34
Q

structural isomers of carboxylic acids

A
  • the carboxyl group can only occur on the end of a molecule
  • carboxylic acids can form isomers with different branches, but the carbon atom in the carboxyl group is always carbon number 1.
  • no number is needed to indicate the location of the functional group in the systematic name
  • name eg
  • 2-methylbutanoic acid
  • 5-methylhexanoic acid
35
Q

what is organic chemistry

A
  • organic chemistry studies the chemistry of carbon-containing compounds known as organic compounds
    • contain carbon
    • typically have hydrogen and oxygen
    • may contain nitrogen, sulfur, phosphorus, halogens (F, Cl, Br, I)
    • exceptions CO, CO2, H2CO3
36
Q

carbon chains

A
  • carbon is the element that is most involved in covalent bonding.
  • carbon is always at the centre of any molecule it is in.
  • when we draw a carbon compound, we first join all the carbon atoms together, then we add the other atoms to the outside of this carbon skeleton
37
Q

sources of organic compounds

A

crude oil

  • Fossil fuel
  • Undergoes fractional distillation which separates hydrocarbons according to their boiling points
  • Non-renewable

plant-based biomass

  • Carbon-based material from plants
  • Renewable source of carbon
  • eg. ethanol from sugar cane
38
Q

making polyethene from sugar

A
  1. Carbon dioxide transforms to glucose in plants (photosynthesis)
  2. Glucose is converted into bioethanol
  3. Bioethanol is used to make bioethene (more environmentally friendly than producing ethene from crude oil)
  4. Bioethene is used to make polyethene (polymer) used to make products

CHEMISTRY U1/2 (15 decks)

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