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chemistry > S3.2 - functional groups: classification of organic compounds > Flashcards

S3.2 - functional groups: classification of organic compounds Flashcards

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1
Q

What is empirical formula?

A

Empirical formula is the simplest whole number ratio of atoms in a compound.

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2
Q

What is molecular formula?

A

Molecular formula is the actual number of atoms in a molecule.
M = (molar mass of empirical formula)n

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3
Q

What is structural formula?

A

Structural formula is a representation of the molecule, showing how atoms are bonded to each other.

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4
Q

What are the 3 types of structural formula?

A
  • Full structural formula
  • Condensed structural formula
  • Stereochemical formula
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5
Q

What is a full structural formula?

A
  • Shows every bond and atom
  • Uses 60, 90 and 180 which is clear, but isn’t the true geometry.
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6
Q

What is a condensed structural formula?

A

Groups atoms together and emits assumed C-H bonds to minimize formula.
CH3CH3

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7
Q

What is stereochemical formula?

A

3D model that shows the position of atoms and groups around a central atom.

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8
Q

What are limitations of the molecular formula?

A

Properties of a compound are determined not only by the atoms it contains, but how they are arranged relative to each other and space.

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9
Q

What is skeletal formula?

A

Shorthand representation of the structural formula, showing all bonds and symbols except C-H bonds.
- C-C bonds are represented by offset lines and position.
- Number of carbon atoms are identified by the vertices where the bond lines meet.

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10
Q

How can you find the number of hydrogen atoms attached?

A

Subtract the number of bonds drawn to the atom from 4.

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11
Q

What are aromatic compounds?

A

Molecules with a benzene ring (C6H6)

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12
Q

What is R?

A

Any alkyl (C2H6), with a general formula of (CnH2n+1)

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13
Q

What is unique about carbon and enables it to form more compounds than the sum of compounds formed by all the other elements?

A

Carbon atoms are able to sp, sp2 or sp3 hybridize.
- This allows carbon to form a variety of different compounds containing single, double or triple bonds.

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14
Q

What is catenation?

A

Carbon has a unique ability to link to itself and form chains of bonded carbon atoms, as well as ring structures such as benzene.

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15
Q

What are functional groups?

A

Atoms or groups of atoms that are present in organic compounds that are responsible for a compounds physical properties and chemical reactivities.

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16
Q

What does saturated and unsaturated mean?

A

Saturated - only contains single bonds.
Unsaturated - contains double or single bonds.

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17
Q

What is a reaction pathway?

A

Each step in a reaction involves a similar reactant from a previous product and involves a functional group inter-conversion in a series of discrete steps.

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18
Q

What makes up an amino acid?

A
  • Amine group (NH3)
  • Carboxylic acid group (COOH)
  • R group
  • Hydrogen
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19
Q

What happens during a condensation reaction between amino acids?

A

Water is lost and a new bond is formed between the acid group of 1 amino acid and the amino group of another (peptide bond).

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20
Q

What is the general formula, suffix name and name of functional group of alkanes?

A
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21
Q

What is the general formula, suffix name and name of functional group of alkenes?

A
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22
Q

What is the general formula, suffix name and name of functional group of alkynes?

A
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23
Q

What is the general formula, suffix name and name of functional group of alcohols?

A
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24
Q

What is the general formula, suffix name and name of functional group of ethers?

A
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25
Q

What is the general formula, suffix name and name of functional group of aldehydes?

A
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26
Q

What is the general formula, suffix name and name of functional group of ketones?

A
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27
Q

What is the general formula, suffix name and name of functional group of carboxylic acids?

A
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28
Q

What is the general formula, suffix name and name of functional group of esters?

A
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29
Q

What is the general formula, suffix name and name of functional group of amides?

A
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30
Q

What is the general formula, suffix name and name of functional group of amines?

A
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31
Q

What is the general formula, suffix name and name of functional group of halogeneoalkanes?

A
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32
Q

What is the general formula, suffix name and name of functional group of arenes?

A
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33
Q

What do functional groups influences?

A
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34
Q

What is a homologous series?

A

Family of compounds in which each successive member differs by CH2 and can be described by a general formula.

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35
Q

What are trends in boiling points of homologous series?

A

Boiling points increase with increasing carbon number due to increased IMF as molecular size increases.

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36
Q

Which IMF is affected?

A

LDF’s increase in strength.

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37
Q

How can functional groups affect volatility?

A

Most –> least volatile:
Alkane / Alkene / Alkyne / Halogeneoalkane / Aldehyde / Ether / Ester / Ketone / Alcohol / Amine / Amide / Carboxylic acid

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38
Q

How can functional groups affect the type of IMF present?

A

LDF –> Dipole-Dipole –> Hydrogen bonding
Alkane / Alkene / Alkyne / Halogeneoalkane / Aldehyde / Ether / Ester / Ketone / Alcohol / Amine / Amide / Carboxylic acid

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39
Q

What do successive homologous series differ by?

A

CH2

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40
Q

What is the IUPAC nomenclature?

A

set of rules used by the International Union of Applied Chemistry to apply systematic names to organic and inorganic compounds

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41
Q

What are the steps in naming compounds?

A
  1. Identify the stem - longest straight chain of carbon
  2. Identify the functional group - determines the suffix (ane for alkanes)
  3. Identify side chains - determines the prefix (methyl for CH3)
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42
Q

How are esters formed?

A

Alkyl group of an alcohol replaces the hydrogen in a carboxylic acid in a condensation reaction

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43
Q

How are ethers formed?

A

Two alkyl groups joined by an oxygen atom

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44
Q

How do you name ethers?

A

Longer chain forms the stem and retains the alkane name (propane) and shorter chains is given the prefix alkoxy (methoxy for 1 carbon)

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45
Q

How do you name esters?

A

Salts take the stem of the name (ethyl) and the alcohol forms the suffix (propanoate)

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46
Q

What are the 3 possible parts of IUPAC nomenclature?

A
  1. Prefix - position, number and name of substituents
  2. Stem - number of carbon atoms in the longest chain
  3. Suffix - class of compound determined by functional group
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47
Q

What are structural isomers?

A

molecules that have the same molecular formula but different arrangements of the atoms so have different chemical and physical properties

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48
Q

What are the properties of branched structural isomers?

A

the more branching present, the lower the melting point due to reduced surface contact which weakens the strength of the LDF’s between neighboring molecules (instantaneous and induced dipoles)

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49
Q

What are the 4 types of structural isomers?

A
  • branched
  • unbranched
  • positional
  • functional group
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50
Q

How are branched structural isomers used within the industry?

A

branched chain isomers burn more smoothly in internal combustion engines
- factions with more branched chains are premium - higher octane number

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51
Q

What are positional structural isomers?

A

isomers with the same molecular formula and functional group, but in a different position

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52
Q

What are functional group structural isomers?

A

isomers with the same molecular formula but a different functional group

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53
Q

What are primary compounds?

A

the C attached to the OH group is attached to 1 other C atom

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54
Q

What are secondary compounds?

A

the C attached to the OH group is attached to 2 other C atoms

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55
Q

What are tertiary compounds?

A

the C attached to the OH group is attached to 3 other C atoms

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56
Q

Why are numbers assigned to ring positions of the substituted benzene?

A

So that the lowest numbers possible are obtained.

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57
Q

When are substituted benzene compounds formed?

A

Formed when H molecules in a Benzene atom are replaced by a halogen group or a functional group, including amino (NH2) or nitro (NO2).

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58
Q

Why are there no structural isomers for monosubstituted benzene?

A

All 6 positions in the hexagonal carbon ring are identical.
- However, 3 structural isomers for bisubstituted benzene does exist.

59
Q

What does there being 3 disubstituted benzene structural isomers show?

A

Provides additional support for the accepted model of Benzene where it exists as a hexagonal ring with delocalised pi bonds and all C-C bonds having equal length.

60
Q

What are stereoisomers?

A
61
Q

What is isomerism?

A
62
Q

What is a structural isomerism?

A
63
Q

What is stereoisomerism?

A
64
Q

What are the 2 types of stereoisomerism?

A
65
Q

What is configurational isomerism?

A
66
Q

What is conformational isomerism?

A
67
Q

What are the 2 types of configurational isomerism?

A
68
Q

What is cis-trans and isomerism?

A
69
Q

What is optical isomerism?

A
70
Q

Why can conformational isomers not be isolated seperately?

A
71
Q

What molecules can cis-trans isomers occur with?

A
72
Q

Why can isomers rise from double-bonded molecules?

A
73
Q

Why can isomers rise from cyclic molecules?

A
74
Q

What is a chiral?

A
75
Q

What are alternate names for a chiral?

A
76
Q

What are enantiomers?

A
77
Q

What does non-superimposable mean?

A
78
Q

What are diastereomers?

A
79
Q

What is a polarizer?

A
80
Q

What is plane-polarized light?

A
81
Q

What is a polarimeter?

A
82
Q

What is an analyser?

A
83
Q

What does it mean to be optically active?

A
84
Q

What is a racemic mixture?

A
85
Q

What does it mean to be optically inactive?

A
86
Q

How do 2 enantiomers of a chiral compound rotate?

A
87
Q

What is asymmetric synthesis?

A
88
Q

What are 3 types of analysis?

A
  1. Qualitative analysis
  2. Quantitative analysis
  3. Structural analysis
89
Q

What is qualitative analysis?

A

Detection for the presence, not the quantity of a substance in a mixture.

90
Q

What is quantitative analysis?

A

Measurement of the quantity of a particular substance in a mixture.

91
Q

What is structural analysis?

A

Description on how atoms are arranged in molecular structures.

92
Q

What are 3 common instrumental methods of analysis?

A
  • Mass spectrometry
  • Infrared spectroscopy
  • Nuclear magnetic resonance spectroscopy
93
Q

What is mass spectrometry used for?

A

Used to determine the relative atomic mass and molecular mass; the fragmentation pattern can be used as a fingerprint technique to identify unknown substances or for evidence of the arrangements of atoms in a molecule.

94
Q

What does MS cause?

A

MS of organic compounds can cause fragmentation of the molecules.

94
Q

What happens during mass spectrometry?

A

A parent ion breaks down into smaller ions to create a fragmentation pattern which provides useful information about the mass of individual atoms (RAM) and the abundance of relative isotopes.

95
Q

How do you work out the molecular ion using a mass spectra?

A

Peak furthest to the right.

96
Q

When is a molecular ion formed?

A

The molecular ion, or parent ion is formed when a molecule loses 1 electron, but otherwise remains unchanged.

97
Q

What are the charges of peaks in a mass spectra?

A

Have to be +, otherwise they would not be detected.

98
Q

What happens to radicals in MS?

A

Radicals aren’t +, so are not detected by MS and disappear into the atmosphere.

99
Q

What is infrared spectroscopy?

A

Used to identify the type of bond present in a molecule.

100
Q

What are the relative numbers like for IR in terms of energy, wavelength and frequency?

A

Frequency - large
Energy and wavelength - small

101
Q

What can be identified from IR spectra?

A

It can identify the type of bond present in a molecule which can be determined by wavenumber and frequency.

102
Q

What is wavelength?

A

The distance between 2 successive crests or troughs.

103
Q

What is frequency?

A

Number of waves passing a point per second.

104
Q

How do you calculate wave speed?

A

Wave speed = frequency x wavelength

105
Q

What is wavenumber?

A

Measure of frequency commonly used in IR spectroscopy (cm-1).
- Number of peaks that occur in 1cm.

106
Q

How do you work out the frequency of a wave in terms of wavenumber (cm-1)?

A

Frequency (cm-1) = 1 / wavelength (cm)

107
Q

What are ER waves?

A

Electromagnetic waves that transfer energy and carry information by interacting substances in a different way.

108
Q

How do radio waves interact with molecules?

A

Radio waves can be absorbed by certain nuclei, causing them to reverse their nuclear spin, telling us about the hydrogen environments in a molecule.

109
Q

How do micro waves interact with molecules?

A

Micro waves cause molecules to increase their rotational energy and tell us about their bond lengths.

110
Q

How does infrared radiation interact with molecules?

A

IR radiation is absorbed by bonds and causes them to stretch or bend in a specific way that tells us about the bond.

111
Q

How does visible light and UV interact with molecules?

A

UV and visible light produces electronic transitions and tell us about energy levels in an atom.

112
Q

How do x-rays interact with molecules?

A

X-rays have a wavelength similar to bond lengths in crystals which can be used to determine the crystal structure.

113
Q

What does the natural frequency of a chemical bond depend on?

A
  • Bond strength
  • Masses of atoms
114
Q

What happens when molecules absorb IR?

A

Absorbing IR excites the bonds in molecules.
- The energy needed to excite the bonds in a molecule occurs in the IR region.

115
Q

When will a bond interact with IR?

A

A bond in a diatomic molecule will only interact with IR if it is polar as only polar bonds will absorb IR as the presence of partial - and + charges allows the electric field component of the EM to excite the vibrational energy of the molecule.

116
Q

Which bonds are most common and why?

A

C-O / C–O / O-H / C-H
- These bonds absorb IR strongly

117
Q

When will a bond in a diatomic molecule react?

A

If it is polar, it will react with the electric field and absorb IR.

118
Q

What does a change in vibrational energy produce?

A

Changes in vibrational energy produces a corresponding change in the dipole moment in a molecule.

119
Q

What does intensity of absorption depend on?

A

Polarity of the bond.

120
Q

Why do symmetrical non-polar bonds in N—N and O–O no absorb radiation?

A

They do not interact with the electrical field.

121
Q

What is the difference between a simple or complex molecule when they vibrate?

A

Simple molecule - bond stretches
Complex molecule - bond stretches and bends

122
Q

What are the 3 fundamental frequencies of polyatomic atoms (water) ?

A
  • Symmetric stretch ( same direction)
  • Asymmetric stretch ( opposite direction)
  • Symmetric bond
123
Q

What are the 4 modes of vibration of symmetric linear molecules (CO2)?

A
  • Inactive IR stretch (no change in dipole as molecule remains symmetrical)
  • Asymmetric stretch (temporary dipole)
  • 2 symmetric bonds (into/out of the plane of the page and is a temporary dipole).
124
Q

What is a fingerprint region?

A

Region that can be used to identify an unknown compound.

125
Q

What is the order of regions from high to low wavenumber?

A

1) C-H / O-H / N-H (single bond to H stretches)
2) C—C / C—N (triple bond stretches)
3) C–C / C–O ( double bond stretches)
4) Fingerprint region

126
Q

What are examples of short-wave radiation?

A

UV and visible light

127
Q

What are examples of long-wave radiation?

A

IR

128
Q

What is the global warming potential?

A

Compares the amount of IR energy absorbed by a gas compared to 1 tonne of CO2 over a period of time.

129
Q

What is the greenhouse effect?

A

Short-wave radiation is absorbed by the Earth’s surface and emitted as long-wave radiation, which is absorbed by greenhouse gases and re-emitted back into the atmosphere, keeping the Earth warm.

130
Q

What does the global warming potential depend on?

A
  • How effective the individual gas atoms are at absorbing IR
  • Atmosphere lifetime of a gas
131
Q

How do you work out the structure of a compound?

A
  1. Look at IR spectra graphs.
  2. Identify peaks and waveneumber.
    3 Use data booklet to work out which bonds are present.
132
Q

What is proton nuclear magnetic resonance spectroscopy (HNMR)?

A

Used to show the chemical environment of Hydrogen atoms in a molecule, giving structural information about a molecule.

133
Q

What is MRI?

A

Uses NMR in the presence of a powerful magnet where radio waves are used to generate electrical signals which produce either 2D or 3D images.

134
Q

What is nuclear magnetic resonance spectroscopy?

A

Used to find the structure and shape of a molecule by identifying different protons in a molecule which are bonded to different atoms.

135
Q

What 4 things can be deduced from NMR?

A
  1. Number of peaks in the spectrum
  2. Position or chemical shift of each peak
  3. Size or integrated area of each peak
  4. Splitting pattern observed for each peak
136
Q

How does HNMR show the different chemical environments?

A

Number of peaks observed in a spectrum = number of different chemical environments

137
Q

What is a chemical shift?

A

Position where a signal appears in a NMR spectrum ,measured in ppm

138
Q

What is the link between chemical shifts and the position of the H atoms in a molecule?

A

The closer the atoms are to the OH group, the higher the chemical shift observed as the high electronegativity of O pulls electrons away from H, so nuclei become deshielded and more susceptible to the effects of the external magnetic field

139
Q

What does the area under the curve depend on?

A

Number of nuclei in a chemical environment

140
Q

What is an integrated trace?

A

Shows the relative number of H atoms in a chemical environment

141
Q

How can we determine the number of peaks caused by splitting?

A

n+1, where n is the number of neighboring H atoms

142
Q

How is the intensity of peaks determined?

A

Following Pascall’s triangle

143
Q

What else should we consider when analyzing NMR?

A
  • Protons bonded to the same atom do not interact with each other as they are equivalent and act as a group.
  • Protons on carbon atoms that are not next to each other do not interact with each other as the magnetic fields are too far apart to interact with spin-spin coupling
  • OH atoms don’t undergo spin-spin coupling with H of neighbor atoms as it isn’t split by other atoms.

chemistry (22 decks)

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