Introduction to organic chemistry Flashcards
1
Q
Define hydrocarbons.
A
Hydrocarbons are compounds that are made up of carbon and hydrogen only.
2
Q
Define functional group.
A
A functional group is an atom or a group of atoms in an organic molecule which determines the characteristic chemical reactions. Organic molecules are classified by the dominant functional group.
3
Q
Define homologus series.
A
Homologus series is a group of organic compounds having the same functional group, the same general formula and similar chemical properties.
4
Q
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What is a general formula?
A
The general formula is the formula that represents a homologus series of compounds using letters and numbers. For example the general formula of alkanes are CnH2n+2
5
Q
What is the general formula for alkenes?
A
CnH2n
6
Q
What is the general formula of halogenoalkanes?
A
CnH2n+1X
where x=f,Cl,Br,I
7
Q
How do we name halogenoalkanes?
A
The prefixes fluoro,Chloro,Bromo and Iodo are used. For example Chloropropane.
8
Q
What is the general formula for alcohol?
A
CnH2n+1OH
9
Q
How do we name organic molecules with alcohol functional group?
A
Alcohol is named by identifying the longest straight carbon chain containing the -OH group. The -ane suffix is replaced with -anol and the location of the -OH group on the chain is designed by a number. For example propan-1-ol.
10
Q
What is the general formula for aldehydes?
A
CnH2n+1CHO
11
Q
How do we name aldehydes?
A
Aldehydes take their name from their parent alkane chains. The -e is removed from the end and is replaced with -al. For example propanal. Aldehyde is always at carbon 1. Aldehyde has greater priority over hydroxyl and amino group and ketones. Carboxylic acid has more priority over aldehydes.
12
Q
What is the chemical formula for ketones?
A
CnH2n+1COCmH2m+1
13
Q
How do we name ketones?
A
The name of a ketone ends with the suffix “one”.
A number is used to denote the carbon atom on which the carbonyl group is bonded.
The first ketone in the homologous series is therefore propane.
14
Q
What is the first ketone in the homologous series?
A
The first ketone in the homologous series is propanone.
15
Q
What is the general formula for carboxylic acids?
A
CnH2n+1COOH
16
Q
How do we name carboxylic acids?
A
- Select the longest carbon chain containing the
carboxyl group. The -e ending of the parent alkane
name is replaced by the suffix -oic acid. - Aromatic carboxylic acids (i.e., with a CO2H
directly connected to a benzene ring) are named
after the parent compound, benzoic acid.
17
Q
What is the general formula for an ester?
A
CnH2n+1COOCmH2m+1
18
Q
How do we name esters?
A
19
Q
What is the general formula for amines?
A
CnH2n+1NH2
20
Q
What is the name of the functional group of aldehydes?
A
Aldehydes have the carbonyl functional group at the end of their carbon chain.
21
Q
What is the name of the functional group of ketones?
A
Ketones are molecules which contain the carbonyl functional group in the middle of the carbon chain.
22
Q
What is the IUPAC system?
A
International Union of Pure and Applied Chemistry system for the standardised naming of organic compounds.
23
Q
What is the functional group of nitriles?
A
A nitrile is an organic compound consisting of an alkyle group with a cyanide group (-CN) attached to it.
24
Q
What is a cynaide group?
A
The cynaide group consists of a carbon atom and a nitrogen atom linked by a triple covalent bond.
25
What is the empirical formula?
The empirical formula shows the simplest whole number ratio of the elements present in one molecule of the compound. For example emeprical formula of glucose is CH2O.
26
What is a molecular formula?
The molecular formula shows the actual number of each type of atom in a molecule. For example the molecular formula of glucose is C6H12O6.
27
What is the structural formula?
The structural formula shows how many, and the symbols of, atoms bonded to each carbon atom in an organic molecule. The structural formula of propane: CH3CH2CH3
The structural formula of propene:
CH3HC=CH2
(c-c double bonds are shown in structural formula)
28
How can we calculate molecular formula using emperical formula and relative molecular mass?
Example:
Mr=42 and Emperical formula=CH2.
Divide Mr by Emperical formula. 42/14=3
Multiply emperical formula by 3= C3H6
29
What is the displayed formula?
The displayed formula shows a 2D representation of an organic molecule, showing all its atoms (by their symbols) and their bonds (by short single, double or triple lines).
30
What is a skeletal formula?
The skeletal fomula is a simplified displayed formula with all C-H bonds removed.
31
What is an aliphatic structure?
An aliphatic compound is a straight chain or branched chain organic compound and also include cyclic compounds that do not contain a benzene ring.
32
What are alkynes?
Alkynes are hydrocarbons which contain carbon-carbon triple bonds. Their general formula is CnH2n-2 for molecules with one triple bond (and no rings)
33
What is an aryl compound?
An aryl compound contains at least one benzene ring.
34
What is a benzene ring?
A benzene molecule has 6 carbon atoms arranged in a hexagon, with each carbon atom bonded to one hydrogen atom. The carbon atoms are linked by bonds that alternate between single and double bonds,
35
What is a saturated hydrocarbon?
Saturated hydrocarbons are hydrocarbons which contain single bonds only resulting in the maximum number of hydrogen atoms in the molecule.
36
What is an unsaturated hydrocarbon?
Unsaturated hydrocarbons are hydrocarbons which contain carbon-carbon double or triple bonds.
37
What is a reaction mechanism?
A reaction mechanism is the series of steps that take place in the course of the overall reaction.
38
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What is homolytic fission?
Homolytic fission is breaking a covalent bond in such a way that each atoms takes an electron from the bond to form two radicals. This takes place when electronegativity difference is 0 or less than 0.5.
39
What is homolytic fission represented by?
Homolytic fission is represented by half curly arrow or fishing arrow.
40
What is required for homolytic fission?
Sunlight is required for homolytic fission except chlorine where UV light is needed. The energy of one UV photon is equal to the bond energy of chlorine molecule.
41
What is formed in homolytic fission?
The species produced when a bond breaks homolytically are called free radicals. All free radicles have an unpaired electron (represented by the dot) and are very reactive. If free radicles are involved in a reaction it will be highly exothermic.
42
What is heterolytic fission?
Heterolytic fission is breaking a bond in such a way that the more electronegative atom takes BOTH electrons from the bond to form negative ion and leave behind a positive ion. Cationsand anions are formed. Takes place if electronegativity difference is greater than 0.5.
| More common than homolytic fisson
43
What is heterolytic fission represented by?
Represented by a full arrow.
44
What is an electrophile?
An electrophile is an electron-deficient species that acts as an electron pair (one electron) acceptor. They carry a positve charge or have an empty orbital. They are also called lewis acids.
45
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What is an electrophillic reaction?
Electrophillic refers to reactions that involve an electrophile.
46
Give examples of electrophiles.
H+,CH3+,c2h5+,Cl+,Br+,I+,NO2+,
CL2,Br2,I2, (With respect to alkenes)
AlCl3,BCl3 (empty orbitals)
No Metals (they form ionic bonds)
47
What is a nucleophile?
Nucleophile is an electron-rich species that can donate a pair of electrons. Nucleophile contain a negative charge or have a lone pair. They are also called lewis bases.
48
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What is a nucleophillic reaction?
A nucleophillic reactions refers to reactions that involve a nucleophile.
49
Give examples of nucleophiles.
Cl-,Br-,I-,OH-,CN-,NH3,C2H5O-,H20
Ethanoate ion
Ethoxide ion
50
What is the synthetic route?
Hydrocarbon →Alchohol →Aldehyde or ketone →Carboxylic Acid (Only From Aldehyde)
Forward Arrow (Oxidation)
Backwards Arrow (Reduction)
51
What is oxidation?
An oxidation reaction is a reaction in which oxygen is added, electrons are removed or the oxidation number of a substance is increased. In organic chemistry it often refers to the addition of oxygen and/or removal of hydrogen atoms.
52
How do we represent oxidising agents?
In equations for organic redox reactions, the symbol [O] can be used to represent one atom of oxygen from an oxidising agent.
53
What is a reduction reaction?
A reduction reaction is a reaction in which oxygen is removed, electrons are added or the oxidation number of a substance is decreased.
In organic chemistry it often refers to the removal of oxygen or addition of hydrogen atoms to a substance.
54
How do we represent reducing agents?
In equations for organic redox reactions, the symbol [H] can be used to represent one atom of hydrogen from a reducing agent
55
What is an example of a strong oxidising agent?
KMno4 Potassium Permanganate
56
Give an example of a weak oxidising agent
K2Cr2O7 Pottasium Dichromate
57
Give an example of a strong reducing agent.
LiAlH4 Lithium Aluminium Hydride
58
Give an example of a weak reducing reagent.
NaBH4 Sodium Borohydride
59
What is an oxidising agent?
Substance that oxidises another atom or ion by causing it to lose electrons. (It itself gets reduced-gain electrons)
60
What is a reducing agent?
Substance that reduces another atom or ion by causing it to gain electrons. (it itself gets oxidised-loses electrons)
61
When do we use a weak oxidisng/reducing agent?
If one step reduction reduction or oxidation, weak oxidising/reducing agent is used.
62
When do we use a strong oxidising/reducing agent?
If more than one step oxidation or reduction, strong oxidising/reduction agent is used.
63
What is isomerism?
Compounds which have the same molecular formula but differ in physical and chemiscal properties are called isomers and the phenomena is called isomerism.
64
What is structural isomerism?
Structural isomerism are compounds that have the same molecular formula but different structural formula. The three types are: Chain,Functional and positional.
65
What is chain isomerism?
Compounds have which have the same molecular formula but their longest hydrocarbon chain is not the same. The structure of the "carbon skeleton" is changed. This is cause by branching.
66
What is position isomerism?
Positional isomers arise from differences in the position of a functional group in each isomer. The functional group can be located on different carbons. Cannot occur in aldehydes. Position isomerism in ketones starts from carbon 5.
67
What is functional isomerism?
When different functional groups results in the same molecular formua, functional group isomers arise.
The isomers have very different chemical properties as they have different funtional groups.
Alkenealways produce cycloalkanes after functional isomerism. Aldehydes always covert into ketons after functional isomerism. Ethanol produces ether after functional isomerism.
68
What is sterioisomerism?
Sterioisomerism are compounds that have the same atoms bonded to each oher in the same way, but with a different arrangement of atoms in space so that the molecules cannot be super imposed on each other.
69
What is geometrical isomerism?
Geometrical isomerism is seen in unsaturated or ring compound with the same moleular formula and order of atoms (the atoms are connected similarly to each other) but different shapes. Arises from a lack of free rotation about a double bond (due to the presense of π bond) or a ring structure because there is a lack of rotation about c-c single bonds which make up the ring.
70
What are the two types of geometrical isomerism?
Cis and Trans Isomerism
71
What is cis isomerism?
Cis isomers have functional groups on the same side of the double bond/carbon ring.
72
What is trans isomerism?
Trans isomers have functional groups on opposite sides (diagonally) of the double bond/carbon ring.
73
When is geometrical isomerism not possible?
Geometrical isomerism is not observed in a molecule if either of the doubly bonded carbon atoms has two similar groups.
| It would be a structural isomer.
74
What formula can be used to calculate the total geometrical isomers if more than one double bond is present in the molecule:
2^n where n=no of double bonds
but be careful if the double bonded carbon atom has two similar groups. For e.g. CH2=CH
75
How can we identify geometrical isomerism through Mr?
If four different groups are attached with a double bonded carbon atom then we need to consider Mr of the groups and apply them vertically. If heavier masses lie diagonally its trans. If they lie on the same side its cis.
76
Can geometrical isomerism occur in cyclic alkenes?
In cyclic alkenes only cis isomer is possible because of bond pair bond pair repulsion, tran is not possible.
| Also possible in skeletal structure.
77
What is optical isomerism?
Optical iosomers arise when carbon atom in a molecule is bonded to four different atoms or groups of atoms. The carbon atom is "asymmeteric" as there is no plane of symmetry in the molecule and is called the chiral centre of the molecule.
78
How do we represent a chiral carbon?
A chiral carbon is represented by asterik. *
79
What are optically active compounds?
Compounds which contain chiral carbon are called optically active compound.
80
What are eneantiomers?
A pair of optically active molecules whose mirror images cannot be superimposed is called enantiomers.
81
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How do optical isomers differ from each other?
Optical isomers differ in their ability to rotate the plane of polarised light.
One enantiomer will rotate it clockwise and the other anticlockwise.
82
How can we determine total optical isomers if more than one chiral carbon is present in the molecule?
2^n where n=number of chiral carbons.
83
Are chiral carbons present in cyclic rings?
Chiral carbons are present in unsymmetrical cyclic rings not symmetrical. (see diagram).
Ony take neighbouring groups to determine if chiral carbon is within the region.
84
What is a free radical reaction?
A free radicle reaction is a reaction involving free radicles and is a three step reaction.
1.initiation
2.Propogation
3.Termination
85
Explain the second step in a free radical reaction.
propagation step: The formed free radicle can attack reactant molecules to form even more free radicles. These in turn can again attack other molecules to form free radicles and so on.
86
What is the third step in the free radical reaction?
Termination reaction: Two free radicals react together to form a product molecule.
87
What is the first step in the free radicle reaction?
Initiation step: breaking a covalent bond using energy from ultraviolet (UV) light from the sun to form two free radicals to start a reaction off.
88
Define addition reaction
An addition reaction is a reaction in which two (or more) molecules combine to give a single product with no other products.
For example: C2H4+Br2 =C2H4Br2
89
What is a condensation reaction?
A condensation reaction is a two step reaction in which two organic molecules join together (addition) and in the process eliminate small molecules (such as H20 and HCl( to form the final product.
For example: two organic molecules (alcohol and carboxylic acid) react together and eliminate a small molecule (H2O).
Methanol + ethanoic acid= methyl acetate (C3H6O2) (ester) + water.
90
Define elimination reaction
An elimination reaction is a reaction in which a small molecule (such as H20 and HCl) is removed from a larger reactant molecule.
For example: dehydration of an alcohol by concentrated sulfuric acid. C2H5OH (concentrated H2S04 above arrow)=C2H4+H20
91
Define substitution reaction?
A substitution reaction is a reaction that involves replacing an atom or group of atoms with another atom or group of atoms.
For example:Free radical substitution of alkanes by Cl2 in sunlight
CH4+Cl2 (UV light)= CH3CL + HCl
92
What is a hydrolysis reaction?
A hydrolysis reaction is a reaction in which a compound is broken down by water.(It can also refer to the breakdown of a substance by dilute acid or alkalis).
For example water is used to break down ester into an alcohol and carboxylic acid.
