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CHEMISTRY U3/4 > ORGANIC CHEMISTRY > Flashcards

ORGANIC CHEMISTRY Flashcards

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1
Q

intermolecular forces vs intramolecular forces

A
  • intermolecular forces: bonds between molecules
    • dispersion (NP)
    • dipole - dipole (P)
    • hydrogen bonding (type of dipole-dipole - H bonded to N, O, F)
  • intramolecular forces: bonds within molecules
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2
Q

polar vs non-polar

A
  • polar - uneven electron distribution
  • non-polar - even electron distribution
  • C-H bond is considered non-polar - b/c of low electronegative difference
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3
Q

carbon compounds

A
  • make up 90% of all chemical compounds and form the basis of living systems
  • the study of carbon compounds → organic chemistry
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4
Q

saturated vs unsaturated

A
  • saturated: contains only single C-C bonds (alkanes)
  • unsaturated: contains one or more double/triple C-C bonds (alkenes/alkynes)
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5
Q

hydrocarbons

A
  • carbon is versatile because it can bond in diff ways with different atoms
  • hydrocarbons are the simplest molecules
    • contain only hydrogen and carbon - yet a wide variety of different hydrocarbon structures exist
  • exist in families called homologous series
  • compounds that are members of the same homologous series have
    • similar structures
    • similar chemical properties
    • same general formula
    • patterns in their physical properties
  • the functional groups gives a molecule a particular physical and chemical property
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6
Q

stability of carbon bonds

A
  • the amount of energy required to break a bond indicates how strong it is
  • its great stability enables various carbon compounds to exist
  • Stable bonds have larger bond enthalpies
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7
Q

definition of bond strength

A

is the quantity of energy required to break 1 mole of covalent bonds in the gaseous state

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8
Q

molecular formulas

A

indicate the number and type of atoms of each element

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9
Q

structural formulas

A

show the location of covalent bonds in a molecule

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10
Q

semi-structural formula (condensed)

A
  • indicate the structure without showing all the detail
  • group of atoms that form branches are shown in brackets
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11
Q

skeletal structures

A
  • short-hand version of the structural formula used to represent complex organic molecules
  • parent chain represented by a zig-zag line and only the following are included
    • single double and triple carbon bonds
    • bonds to functional groups
    • bonds within functional groups
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12
Q

isomers

A
  • isomers are molecules that contain the same number and type of atoms (same molecular formula) arranged in different ways
    • have different chemical and physical properties
  • two types of structural isomers
    • chain isomers
      • form when the number in the parent carbon chain changes
      • eg, hexane and 3-methylpentane
    • positional isomers
      • when the functional group is attached to a different carbon in the molecule
      • eg. butan-1-ol, butan-2-ol
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13
Q

alkanes and alkyl groups

A
  • general formula
    • CnH2n+2
  • successive members differ by a -CH2- unit
  • alkanes with more than three carbon atoms can form isomers
  • alkyl groups aka alkyl side chains are named after the alkane they are derived with a -yl ending
  • general formula CnH2n+1
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14
Q

cyclohexane

A
  • is a member of the cycloalkane homologous seires
  • it is a saturated molecule that contains 6 carbon atoms
  • its molecular formula is C6H12
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15
Q

alkenes

A
  • unsaturated hydrocarbon with at least one carbon-carbon double bond giving the general formula CnH2n
  • differ by a -CH2- unit
  • alkenes with 4 or more carbon atoms can have structural isomers where the location of the carbon-carbon double bond changes
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16
Q

degree of unsaturation

A
  • identifies how many double bonds or ring structures a molecule contains
  • the number of hydrogen atoms in a fully saturated hydrocarbon =2n+2 where n= no. of carbon atoms
  • each time a molecule forms a double bond or ring, there are 2 fewer hydrogen atoms present
  • the number of double bond or ring equivalents in a molecule can be calculated using the formula:
  • degree of unsaturation = no of double bond or ring equivalents
    • = maximum no of H possible per C - actual number of H per c / 2
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17
Q

benzene

A
  • an unsaturated cyclic hydrocarbon molecule
  • only benzene can have circle in the middle for skeletal formula
  • three of the four valence electrons from each carbon atom form covalent bonds - fourth electron is delocalised (shared) around all six carbon atoms
  • when a benzene ring is bonded to an alkyl group or functional group - the ring structure is called a phenyl functional group and has a formula C6H5
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18
Q

haloalkane

A
  • haloalkanes have at least one hydrogen atom replaced with a halogen atom
  • haloalkanes are widely used as flame retardants, refrigerants, propellants, pesticides, solvents and pharmaceuticals
  • halogen and alkyl groups have the same priority
19
Q

alcohols

A
  • alcohols contain a hydroxyl (-OH) functional group
  • can be primary, secondary or tertiary depending on how many alkyl groups are attached to the carbon bonded to the hydroxyl group
  • primary: carbon bonded to -OH is only bonded to one alkyl group
  • secondary: carbon bonded to -OH is bonded to two alkyl groups
  • tertiary: carbon bonded to -OH is bonded to three alkyl groups -> require branching at the carbon atom attached to the OH group
20
Q

primary amines

A

amines contain the amino functional group (-NH2) for primary amines - other types of amines not covered

21
Q

carbonyl groups

A
  • consist of a carbon atom connect to an oxygen atom by a double bond
  • all atoms bonded to the carbon atom are in a plane and the angles between bonds are 120 degrees
  • non-bonding electron are not incl in structural formulas
22
Q

aldehydes

A
  • contain a carbonyl group at the end of a hydrocarbon chain
  • carbon functional group in an aldehyde is always written as -CHO at the end of the semi-structural formula of aldehydes
  • the simplest aldehyde is methanal HCHO is commonly known as formaldehyde
  • when naming, the e at the end is replaced with an - al
  • carbon atom on the aldehyde group is always carbon number 1
23
Q

ketones

A
  • the ketone in the carbonyl carbon is attached to two other carbon atoms and is never at the end of a molecule
  • the carbon functional group in a ketone is written as CO
  • -e is replaced with suffix -one
  • number is inserted before -one to indicate the number to which the carbonyl group is attached to
24
Q

carboxylic acid

A
  • contain the carbonyl functional group which itself consists of a carbonyl and a hydroxyl group
  • often written as -COOH in semi-structural formula is always located at the end of a hydrocarbon chain
  • when a carboxylic acid reacts w a strong base - salt and water are produced
  • the anion in the salt is named by replacing the -oic part if the name with -oate
  • conjugate base to a carboxylic acid is called a carboxylate ion
25
Q

primary amides

A
  • primary amides contain a carbonyl functional group attached to an amide functional group
  • similar to the carboxyl group except the -Oh is replaced with -NH2
  • amide functional group -NH2 and located at the end of the hydrocarbon chain
26
Q

esters

A
  • are produced by reacting a carboxylic acid with an alcohol and contains the ester functional group
  • carboxylic acid + alcohol → ester + H2O
  • naming convention [alcohol part]+[carboxylic acid part]
    • -yl suffix on alcohol part
    • -oate suffic on acid part
27
Q

naming organic molecules w two functional groups

A
  • use priority table
  • functional group with the highest priority is assigned the lowest possible number and the suffix for this functional group is used
  • the lower priority functional group is indicated by a prefix or alternative name
28
Q

boiling points of organic compounds are influenced by…

A
  • are influenced by
    • size of molecule
    • shape of molecule
    • presence of functional groups
29
Q

dispersion forces

A
  • present in all molecuels
  • stronger in longer and more regularly shaped molecukles
  • the only intermolecular forces in hydrocarbons and hydrocarbon sections
30
Q

dipole dipole attraction

A
  • polar molecules
  • exist where functional groups are present - other than double or triple carbon bonds
  • presence increases boiling point, melting point and viscosity
31
Q

hydrogen bonding

A
  • very strong force
  • present in alcohols, carboxylic acids, amines and amides
  • presence increases boiling point, melting point, and viscosity
32
Q

melting and boiling point of alkanes and alkenes

A
  • only have weak dispersion forces
  • the longer the carbon chain, the greater the strength of dispersion forces between molecules
    • increases the melting and boiling point
33
Q

melting and boiling point of haloalkanes

A
  • haloalkanes are polar
  • presence of dipoles means that haloalkanes have weak dispersion forces and dipole dipole forces
  • dipole-dipole forces are generally higher than those of alkanesewith a similar no of carbon atoms
  • as length of hydrocarbon chain increases, the strength of dispersion forces also increase an therefore the melting and boiling point also increase
34
Q

viscosity definition

A
  • viscosity of a liquid is its resistance to pouring or flowing
  • viscosity of a liquid depends on the intermolecular forces
  • viscosity increases as the forces of attraction between molecules increase (so longer carbon chains have greater viscosity)
  • viscosity of hydrocarbon compounds decrease as temp increases
    • the kinetic energy increases, so molecules move more quickly
    • reduces the amount of contact time between molecular chains and disrupts dispersion forces
35
Q

characteristics of alcohol

A
  • can form hydrogen bonds because of polar oxygen-hydrogen bond in the hydroxy functional group
  • partially positive charged H atom forms a hydrogen bond with the non-bonding electron pair on the oxygen atoms of a neighbouring alcohol molecule increasing melting and boiling point
  • boiling point is affected by the chain length and the position of the OH group
  • as chain length increases, dispersion forces increase
  • branching decreases the effect of dispersion forces as it prevents molecules from packing closely together
    • the more branched the structure, the lower the boiling point
      -** primary alcohols have higher boiling point than corresponding secondary and tertiary alcohols
  • polar bonds have a greater effect when they are exposed
  • alcohols are more viscous than alkanes w the same no. carbon
    • strength of intermolecular hydrogen bonding**
36
Q

carboxylic acids characteristic

A
  • when two carboxylic acids form hydrogen bonds, a dimer is formed
  • a dimer is a stable species that has a molar mass that is double that of a single carboxylic acid molecule
  • when two atoms interact with each other multiple times
  • increased size increases strength of dispersion forces between one dimer and its neighbour
  • carboxylic acids have higher boiling points compared to alcohols
37
Q

amines and amides characteristic

A
  • also form hydrogen bond due to highly polar N-H bond
  • in amines, the hydrogen bonds form between the non-bonding pair of electrons on the electronegative nitrogen atom and the partially positive hydrogen atom on another amine molecule
  • in amides, the hydrogen bonds form between the non-bonding electron pairs on the oxygen atoms of one molecule and the partially positive hydrogen atom on a neighbouring molecule → have higher boiling point
38
Q

aldehydes, ketones and esters characteristic

A
  • are held together by dipole-dipole attractions
  • oxygen is more electronegative than carbon - so cabron-oxygen double bond is polar and can form dipole-dipole attractions with nearby molecules
  • cannot form hydrogen bonds with each other but can form hydrogen bonds with water
  • boiling point of aldehydes of ketones and esters increases as the hydrocarbon chain length increases
    • due to more points of contact between the hydrocarbon chains and an overall increase in the strength of the dispersion forces holding the chains together
39
Q

solubility

A
  • non-polar dissolves non-polar
  • polar dissolves polar
  • liquids that mix are called miscible
  • liquids that do not mix are called immiscible
  • non-polar molecules are insoluble in water
    • alkanes and alkenes are insoluble in water
  • haloalkanes are slightly soluble in water
  • as the length of the carbon chain increases, solubility decreases - the effect of the functional group lessens
    • b/c weak dispersion forces between water molecules and hydrocarbon molecules are not strong enough to overcome the strong attraction between H2O molecules so the two substances remain and separate and don’t mix
40
Q

solubility in organic solvents

A
  • alkanes and some symmetrical haloalkanes are miscible with other non-polar liquids
    • eg. perchloroethylene is a haloalkane that has C-Cl bonds which are polar
    • however, the molecule is symmetrical → so the overall molecule is non-polar
41
Q

solubility of alcohols, amines, amides and carboxylic acid

A
  • smaller molecules are more soluble in water than larger molecules
    • the functional group (containing polar bonds) that reacts with water
  • as chain length increases, the non-polar nature of the molecule also increases
    • alcohol becomes less soluble in water
  • however in organic solvents, as the size of the molecule increases, the solubility also increases
  • the longer the hydrocarbon chains disrupt H- bonds between water molecules
  • hydroxyl group of alcohol can form, H-bonds with water but the hydrocarbon tail can not
    • only dispersion forces occur between the hydrocarbon chain and water molecules
    • not as strong as H- bonds (doesn’t dissolve in water)
42
Q

solubility of aldehydes, ketones and esters

A
  • ketones cannot form hydrogen bonds with each toher
  • can form hydrogen bonds with water
  • small molecules are quite soluble
  • esters don’t form as many H bonds as polar bonds are crowded
43
Q

functional groups vs homologous series

A
  • homologous series: sequence of compounds w same functional group - differ by -CH2- UNIT
  • functional groups: a group of atoms in a molecule that determine some chemical and phhysical properties
44
Q

punctuation rules in IUPAC naming

A
  • commas are used to separate numbers
  • hyphens are used to separate no. from words
  • no space between words

CHEMISTRY U3/4 (11 decks)

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