Organic Chemistry 2 Flashcards
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Term
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Definition
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Terms in organic chemistry
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several terms are used frequently in the study of organic chemistry
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Purpose of introducing and explaining terms
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to facilitate better understanding in the subsequent sections
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Electronic configuration of the carbon atom
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1S2 2S1 2Px1 2Py1 2Pz1
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Carbon atom’s bonding ability
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form four single covalent bonds by sharing electrons with neighbouring atoms (which may be carbon atoms or atoms of other elements) so that the outermost shell of its atom is completely filled
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Direction of the four covalent bonds of carbon
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directed symmetrically in space at an angle of 109°28’ to one another
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Arrangement of the four covalent bonds of a carbon atom
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tetrahedrally
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Term
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Definition
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WHAT IS ORGANIC CHEMISTRY?
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Originally
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Nowadays
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We now define organic chemistry as the chemistry of carbon compounds.
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Apart from a few compounds such as the oxides
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This grouping is justified because of
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VARIETY OF ORGANIC COMPOUNDS
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Organic compounds are made up of
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The presence of numerous organic compounds is due to the following properties of carbon.
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The ease with which carbon combines with hydrogen
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3 The ability of carbon atoms to form single
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We can illustrate the ability of carbon to form a variety of compounds by showing how five carbon atoms can join together to form some compounds.
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Term
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Definition
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CHARACTERISTIC FEATURES OF ORGANIC COMPOUNDS
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Flammability Most organic compounds are flammable and burn exothermically in a plentiful supply of air to yield carbon(IV) oxide and water.
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Thus
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Covalent nature Carbon atoms form stable covalent bonds with one another.
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A carbon-carbon single covalent bond has an energy of $346 kJ mol^{-1}$ This high energy indicates a strong bond.
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Most organic compounds are stable because of the strong carbon- carbon bonds.
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Since they have a covalent nature
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Polarity and solubility Carbon-hydrogen bonds are
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This is because of the almost equal electronegativities of the two elements.
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Most organic compounds are non-polar unless the compounds consist of very electronegative elements like chlorine or groups like the hydroxyl group.
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Since most organic compounds are non-polar
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So most organic compounds are insoluble in water.
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For example
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If an organic compound contains polar groups
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This enables the compound to dissolve in water.
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For example
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Non-polar substances are held together only by Weak intermolecular forces such as the van der Waals forces
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This is why most organic compounds dissolve only in non- polar solvents like benzene or ether.
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Low melting and boiling points Organic compounds generally have lower melting and boiling points than Inorganic compounds.
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This is because these compounds possess relatively weak intermolecular bonds which can be easily broken by heat energy.
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Many of them (mainly those with low relative molecular masses) tend to be volatile and boil at temperatures below $300^{\circ}C.$
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Thennal instability Many organic compounds are thermally unstable
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Reactivity Reactions involving organic compounds tend to be much slower than the ionic reactions commonly encountered in inorganic chemistry.
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They usually require heating
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TERMS IN ORGANIC CHEMISTRY
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Some of these important terms are introduced and explained here to facilitate better understanding in the subsequent sections.
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Electronic configuration of the carbon atom
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This enables the carbon atom to form four single covalent bonds by sharing electrons with neighbouring atoms (which may be carbon atoms or atoms of other elements) so that the outermost shell of its atom is completely filled.
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The four covalent bonds of carbon are directed symmetrically in space at an angle of $109^{\circ}28^{\prime}$ to one another
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Fig. 29.1 Tetrahedral arrangement of the four covalent bonds of a carbon atom.
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Term
Definition
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Homologous series
The numerous organic compounds can be grouped into a comparatively small number of series or families of compounds known as homologous series.
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The simplest series of compounds in organic chemistry is the alkanes.
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We shall study this series to illustrate what a homologous series means.
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The alkanes are a series of hydrocarbons with a general molecular formula of $C_{n}H_{2n+2
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From table 29.1
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Such a family of compounds is known as a homologous series and each individual member is referred to as a homologue.
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A homologous series is a family of organic compounds which follows a regular structural pattern
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Other homologous series include the alkenes
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Homologous series have the following common characteristics.
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Difference between successive homologues Each successive member in such a series differs in its molecular formula by the addition of a $1-CH_{2}-$ group
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Physical properties The physical properties of the members change gradually as the number of carbon atoms per molecule increases.
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For example
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Similarly
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Chemical properties The members show similar chemical properties.
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For example
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They burn in air
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General methods of preparation All members can usually be prepared by using the same general methods
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Table 29.1 Properties of the first ten members of the alkane series.
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Term
Definition
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Table 29.1 Properties of the first ten members of the alkane series.
The following table:"Name of alkane Molecular formula $(C_{n}H_{2m+2})$"
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Alkyl Groups
Alkyl groups Many homologous series can be regarded as being derived from the alkanes by the substitution of one or more of the hydrogen atoms by other elements or groups.
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The univalent group which is formed from an alkane by the loss of a hydrogen atom is known as the alkyl group.
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Thus
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For example
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-Cl.
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The general term alkyl group includes all groups derived from the alkanes by the loss of a hydrogen atom.
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Alkyl groups have a general formula of $C_{n}H_{2n+1}$ They are named after the parent alkanes by replacing the ending -ane by -yl.
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Alkyl groups are given the general symbol
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Sometimes
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Table 29.2 The alkyl groups derived from the first six members of the parent alkane series.
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Term
Definition
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Table 29.2 The alkyl groups derived from the first six members of the parent alkane series.
The following table:"Parent alkane"
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Functional groups
The alkyl group of a compound is fairly inert chemically because of the stability of the carbon-hydrogen bonds.
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The chemical reactivity of an alkyl compound is determined mainly by the substituent group.
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These groups are referred to as the functional groups
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Each functional group has its own characteristic properties.
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When two or more functional groups occur in one molecule
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Thus
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A functional group is an atom
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Table 29.3 gives the general formulae and specifies the functional groups present in many of the homologous series which are derived from the alkanes.
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Table 29.3 The homologous series derived from alkanes.
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Term
Definition
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Table 29.3 The homologous series derived from alkanes.
The following table:"Homologous series"
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Effect of the alkyl and functional groups The functional group determines the basic chemistry of a compound
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For example
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For all alkyl groups larger than $C_{4}H_{9}-$ this opposing effect is sufficient to greatly limit the solubility of the compound in water.
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Saturated and unsaturated compounds
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The alkanes are said to be saturated hydrocarbons.
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For example
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For example
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Ethene and ethyne are the first members of the alkenes and alkynes respectively.
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Both these series can be considered as being derived from the saturated alkanes by the removal of hydrogen atoms and the subsequent introduction of double and triple bonds respectively in their carbon chains.
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The carbon-carbon double and triple covalent bonds represent the functional groups in these series because the availability of electrons in these multiple bonds makes the unsaturated compounds chemically more reactive.
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Compounds containing double or triple bonds between a carbon atom and an atom of another element can also be said to be unsaturated.
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For example
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It is found by determining the percentage composition of the substance by quantitative analysis.
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A more useful formula than the empirical formula is the molecular formula of a substance.
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It indicates the actual numbers of each kind of atoms in a molecule of a substance.
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The molecular formula is deduced from the relative molecular mass of the substance and its empirical formula.
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Structural formula In inorganic chemistry
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This is not the case in organic chemistry where the molecular formula may represent more than one substance.
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A more informative formula called the structural formula is often used to represent a particular organic substance.
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Such a formula indicates how the atoms are arranged within the molecule of a substance.
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The structural formula of ethanoic acid can be represented as follows: H H-C-C= O-H ethanoic acid single covalent bond = double covalent bon = triple covalent bond The formula shows which atoms are linked together and how they are linked by using conventional symbols.
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The structural formula can also be written in a condensed form where the alkyl and functional groups present in the molecule are shown and arranged in the correct order.
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Ethanoic acid can be represented as follows: $CH_{3}COOH$ This condensed structural formula is usually preferred because it indicates clearly the functional groups present in the substance.
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The structural formula can be determined through various spectroscopic methods..
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The structural formula is usually shown as planar a flat molecule.
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for convenience and does not imply A true molecular representation of an alkane
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Term
Definition
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example
should show the actual arrangement of the atoms in space and the angles between the bonds. Thus
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Term
Definition
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carbon(IV) sulphide uses
alkynes
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trichloromethane (chloroform) use
an anaesthetic used in surgical operations.
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tetrachloromethane (carbon tetrachloride) use
an important organic solvent.
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Preparation of Ethene
heating ethanol with excess concentrated tetraoxosulphate (VI) acid at $170^{\circ}C$.
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Reaction stages in ethene preparation
two.
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Reactant ratio for ethyl hydrogentetraoxosulphate(VI) formation
ethanol and the acid in a volume ratio of 1:2 respectively.
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Product of ethanol and tetraoxosulphate(VI) acid reaction
ester
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Alkenes general molecular formula
${C_{n}H}_{2n}$.
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Minimum value of n in alkenes
2
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Difference in hydrogen atoms between alkenes and alkanes
Alkenes contain two hydrogen atoms less than the alkanes.
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Reason for difference in hydrogen atoms
unlike the alkanes which are saturated compounds
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State of ethene
propene
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State of alkenes from $C_{5}H_{10}$ to $C_{17}H_{34}$ at room temperature
liquids.
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State of higher members of alkenes at room temperature
solids.
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Combustion of alkenes
burn with a more luminous and smoky flame than the corresponding alkanes.
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Reason for smoky flame of alkenes
they contain a greater percentage of carbon.
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Reason for higher reactivity of alkenes
The availability of electrons in the double bonds also makes them chemically more reactive than the alkanes.
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Term
Definition
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Polymerization
a process whereby two or more simple molecules are linked to form a much larger molecule.
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Ethene and its derivatives use
undergo polymerization to form important compounds such as poly(ethene) and poly(chloroethene).
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Ethene use
the main source of many important organic compounds such as ethane
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Ethene use
the raw material used for making many important plastics such as poly(ethene);
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Poly(chloroethene) use
also known as polyvinyl chloride (PVC)
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Poly(phenylethene) use
also known as polystyrene
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Term
Definition
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ALKYNES
are unsaturated hydrocarbons with a general molecular formula of $C_nH_{2n-2}$ where n is a positive whole number greater than 1.
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First member of the alkyne series
ethyne or acetylene
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Next member of the alkyne series
$C_3H_4$ or propyne.
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Ethyne preparation
reacting calcium dicarbide with water.
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Calcium dicarbide formula
CaC2(s).
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Water formula
H2O(l).
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Products of calcium dicarbide and water reaction
ethyne gas
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Test for the presence of a triple bond
passing the gas through a solution of silver tetraoxonitrate(V) (silver trioxonitrate(V)) or copper(I) chloride in ammoniacal solution.
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Observation for positive result in triple bond test
a white or reddish precipitate is formed.
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Term
Definition
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ALKANOLS (ALCOHOLS)
are a homologous series of organic compounds with a general molecular formula of $C_nH_{2n+1}OH$ where n is a positive whole number.
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Alkanols functional group
the hydroxyl group
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IUPAC name ending for alkanols
-ol.
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Simplest alkanol
methanol
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Term
Definition
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Naming of alkanols
IUPAC system.
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Naming of alkanols rule 1
Select the longest continuous carbon chain to which the hydroxyl group is attached and name it as the parent alkane.
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Naming of alkanols rule 2
Number the carbon atoms in the chain starting from the end which gives the carbon atom carrying the hydroxyl group the lower number.
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Naming of alkanols rule 3
Replace the -e of the corresponding alkane with -ol.
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Naming of alkanols rule 4
Prefix the name with the number indicating the position of the -OH group.
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Naming of alkanols rule 5
Indicate other substituents or multiple bonds as usual.
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Term
Definition
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Uses of alkanols
Alkanols are very important organic compounds.
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Methanol use
an important industrial solvent.
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Methanol use
raw material for the manufacture of methanal and ethanoic acid.
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Ethanol use
a solvent for varnishes
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Ethanol use
an important industrial solvent.
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Ethanol use
for the preparation of ethanoic acid
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Ethanol use
as a fuel.
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Term
Definition
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Industrial manufacture of ethanol
two main methods: from ethene
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Ethene formula
CH2=CH2(g).
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Water formula
H2O(g).
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Equation for ethanol production from ethene
CH2=CH2(g) + H2O(g) -> CH3CH2OH(g).
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Conditions for ethanol production from ethene
temperature of 300°C
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Fermentation
the process of converting sugar or starch into ethanol by the action of enzymes present in yeast.
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Carbohydrates examples
sugar and starch.
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Enzymes examples
diastase
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Term
Definition
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Okay
I understand.
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I will continue providing the flashcards from the "splitPDF File 419.pdf" document
picking up from where I left
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Test for ethanol
oxidation to ethanoic acid.
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Oxidizing agents for ethanol
acidified potassium dichromate(VI) solution or acidified potassium tetraoxomanganate(VII) solution.
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Observation for positive result in ethanol test
orange colour of the dichromate(VI) ions is discharged and the solution turns green
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Term
Definition
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Maltose formula
C12H22O11(aq).
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Diastase function
present in malt
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Maltose to glucose conversion enzyme
maltase.
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Glucose formula
C6H12O6(aq).
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Zymase function
decomposes the glucose into ethanol and carbon(IV) oxide.
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Ethanol formula
C2H5OH(aq).
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Carbon(IV) oxide formula
CO2(g).
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Term
Definition
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starch to maltose conversion enzyme
diastase.
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Maltose formula
C12H22O11(aq).
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Maltose to glucose conversion enzyme
maltase.
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Glucose formula
C6H12O6(aq).
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Glucose to ethanol and carbon(IV) oxide conversion enzyme
zymase.
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Ethanol formula
C2H5OH(aq).
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Carbon(IV) oxide formula
CO2(g).
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Term
Definition
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Industrial manufacture of ethanol raw materials
molasses
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Enzymes for ethanol production
diastase
