UNIT 10 - Organic Chemistry Flashcards

1
Q

State which nucleophilic substitution mechanism occurs at a faster rate.

A

Sn1 proceeds more quickly than Sn2.

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2
Q

State what colour is an alkane and an alkene under the influence of bromine water.

A

alkene - colourless
alkane - brownish

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3
Q

State the reagents needed to convert nitrobenzene into phenylamine.

A
  1. Tin and concentrated hydrochloric acid.
  2. Heated under reflux in a boiling water bath.
  3. Phenyl ammonium ions reacted with sodium hydroxide.
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4
Q

Distinguish between oxidation of primary alcohols if the desired product is aldehyde vs carboxylic acid.

A

aldehyde - mixture warmed gently and the aldehyde is distilled before it is further oxidized.

carboxylic acid - mixture is first heated under reflux with an excess of the oxidizing agent until all of the alcohol is converted into the carboxylic acid with the pure product obtained by distillation.

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5
Q

State the most common addition polymers and their industrial names.

A

Polychloroethene - PVC

Polytetrafluoroethene - PTFE, Teflon

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6
Q

Define the nitration of benzene.

A

Substitution of -H by -NO2 to form nitrobenzene C6H5NO2 using nitrating mixture (concentrated nitric and concentrated sulfuric acid).

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7
Q

Define configurational isomerism.

A

Can be interconverted only by breaking covalent bonds (cis/trans & optical).

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8
Q

State the two circumstances under which the cis/trans isomers arise.

A
  • double bonded molecules - free rotation not possible because it would push the p orbitals out of position and the pi bond would break.
  • cyclic molecules - ring restricts rotations and the bond angles are already strained.
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9
Q

Describe the mechanism of the Sn2 reaction with its molecularity and characteristic features.

A

Substitution nucleophilic bimolecular mechanism.

Involves a primary halogenoalkane attacked by a nucleophile

Forms a transition state where the carbon is weakly bonded to both the halogen and nucleophile

then the carbon-halogen bond breaks heterolytically releasing the halogen and forming the alcohol product inversion of the arrangement of the atoms around the carbon atom.

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10
Q

Define and state the reaction formula for esterification.

A

Reaction of alcohol with carboxylic acid in the presence of an acid catalyst (concentrated sulfuric acid) to form an ester and water.

ROH + R’COOH -H+-> R’COOR + H2O

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11
Q

Define homolytic fission.

A

A bond breaks by splitting the shared pair of electrons between the two products and thus produced two free radicals, each with an unpaired electron.

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12
Q

State the reducing agents for the reduction of carboxylic acid and a ketone.

A

carboxylic acid - LiAlH4 - lithium aluminum hydride

ketone - NaBH4 - sodiumborohydride

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13
Q

Define stereoisomerism.

A

Different spatial arrangements of atoms in molecules.

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14
Q

Define a carbocation.

A

Positive ion with the charge centered on a carbon atom.

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15
Q

State the utility of bromine water.

A

Used to distinguish between saturated and unsaturated compounds.

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16
Q

Define the steric hindrance.

A

A bulky molecule (with multiple bonds to compounds or groups other than hydrogen) slowing down or preventing another molecule from efficiently finding the desired bond site in a reaction.

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17
Q

State the product and catalyst of an alkene reacting with hydrogen.

A

Alkane (through hydrogenation)

nickel catalyst
150 degrees Celsius.

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18
Q

List the rules of the priority of substituents in cis/trans isomers.

A
  1. atom bonded to the carbon of the double bond with higher atomic mass has the higher priority.
  2. same rule to the next bonded atom if the atoms bonded first are the same (longer hydrocarbon chains have higher priority).
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19
Q

Define a structural isomer.

A

The same molecular formula with different arrangement of atoms.

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20
Q

Describe the electrophilic substitution in benzene.

A

Electron deficient species (electrophiles) are attracted to the electrons above and below the benzene ring and so can substitute the H atoms without needing to overcome the delocalization energy.

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21
Q

What properties will increase up (with increasing carbon number) the homologous series of compounds.

A
  • boiling point - instantaneous induced dipoles and thus stronger LDF
  • density
  • viscosity
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22
Q

Define conformational isomerism.

A

Interconverted by free rotation about sigma bonds.

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23
Q

State the hybridization and angle of the carbon atoms in benzene.

A

120 degrees
sp2

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24
Q

Define a heterolytic fission.

A

Bond breaking with both the shared electrons going to one of the products.

Producing two oppositely charged ions.

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25
Q

State the product of an alkene reacting with a hydrogen halide (HCl/HBr).

A

halogenoalkanes

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26
Q

State the general reactivity of alkanes and mention the reactions they undergo.

A

Very unreactive.

  • combustion
  • free-radical substitution with halogens to form halogenoalkanes.
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27
Q

Define the addition polymers and list example.

A

Polymers formed from several thousand alkene monomers under certain conditions (e.g. high pressure)

polyethene H2C=CH2

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28
Q

State the product of a polymerization reaction of ethene.

A

polyethene

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29
Q

Distinguish between the primary, secondary and tertiary alcohols.

A

Primary - 1R group attached to the carbon atom

Secondary - 2R groups attached to the carbon atom

Tertiary - 3R groups attached to the carbon atom

Same rule for halogenoalkanes and amines.

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30
Q

State the functional group, its name, the suffix and the general formula for ketones.

A

R-C=O
R’-carbonyl-anone
R-CO-R’

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31
Q

Define resolution of the racemic mixture.

A

Separation of the two enantiomers based on their different chemical and physical properties.

32
Q

Define a nucleophile.

A

Small electron rich molecules or ions with non-bonding pair of electrons.

33
Q

Describe the mechanism of Sn1 reactions.

A

Involves tertiary halogenoalkanes.

Presence of three alkyl groups around the carbon-halogen bond causes steric hindrance.

  1. Ionization of the halogenoalkane by breaking its carbon-halogen bond heterotically.
  2. Formation of the carboncation intermediate as the halide ion is detached.
  3. Nucleophilic attack forming a new bond.
34
Q

State the phases of free radical substitution.

A
  1. initiation - UV light supplies energy to break the weak Cl-Cl bond through homolytic fission and form Cl free radicals.
  2. propagation - as the free radicals are very energetic they react to form another radical - methyl radical which will in chain reaction form chloromethane.
  3. termination - fusion of leftover radicals.
35
Q

State the defining characteristic of greenhouse gases.

A

Absorption of infrared radiation and thus contribution to global warming and climate change.

36
Q

Define an addition reaction.

A

Two reactants combine to form a single product.

A characteristic of unsaturated compounds containing double or triple bonds.

37
Q

State the solvent required in the Sn2 mechanism.

A

polar, aprotic solvents

like propanone (CH3)2CO

38
Q

State the functional group, its name, the suffix and the general formula for esters.

A

=O-C-O-R
ester-anoate
R-COO-R’

39
Q

State the functional group, its name, the suffix and the general formula for arenes.

A

ring aromatic structure
phenyl
-benzene

40
Q

State the functional group, its name, the suffix and the general formula for amides.

A

=O-C-NH2
carboxyamides
-anamide

41
Q

Define a racemic mixture.

A

Containing equal amounts of two enantiomers - optically inactive.

42
Q

Define a protic solvent.

A

Containing -OH or -NH and thus being able to form hydrogen bonds thus stabilizing the positively charged intermediate by solvation involving ion-dipole interactions.

For example:
water, alcohols and carboxylic acids

43
Q

Describe and state the general formula for the nucleophilic substitution reaction.

A

RBr + OH- -> ROH + Br-

The carbon-halogen bond is polar and so the reaction results in C atom being electron deficit d with a small positive charge and the halogen atom with a small negative charge,
the hydroxide ion has a free pair of electrons which is attracted to the positively charged C atom and bonds to it breaking heterolytically the C-X bond as the halide ion leaves.

44
Q

Distinguish cis and trans isomers.

A

Two highest priority groups on the same side of the double bond - Z isomer - cis - ZUSAMMEN

Two highest priority groups on the opposite side of the double bond - E isomer - trans - ENTGEGEN

45
Q

Define an aprotic solvent and a consequence of using it.

A

Not able to form hydrogen bonds as they do not contain -OH or -NH bonds, although they may have strong dipoles.

Will solvate the metal cation (Na+) rather than the nucleophile (OH-) and so the unsolvated, bare nucleophile has a higher energy state and thus increases the reaction rate.

46
Q

Distinguish and define enantiomers from diastereomers.

A

Enantiomer - opposite configurations at all chiral centers and mirror images of each other.

Diastereomers - opposite configurations at some but not all chiral centers thus not mirror images of each other.

Enantiomers have the same chemical and physical properties while diastereomers differ in them.

47
Q

Define catenation.

A

Process in which many identical atoms are joined together by covalent bond producing straight chain, branched or cyclic structure.

48
Q

State the formula for a complete combustion of hydrocarbons.

A

CxHy + ((x+y):4)O2 -> xCO2 + y/2 H2O

very exothermic

49
Q

State the reason for carbon monoxide being a toxin to humans.

A

It combines irreversibly with the hemoglobin in the blood and prevents it from carrying oxygen.

50
Q

State the mechanism of oxidation of secondary alcohols.

A

Secondary alcohol - [O] -> ketone + H2O

51
Q

State the Markovnikov’s.

A

In an addition of hydrogen halide to asymmetric alkenes the electrophilic portion of the reagent will attach to the carbon that is already bonded to the greater number of hydrogens.

52
Q

State the mechanism of nucleophilic substitution the secondary halogenoalkanes undergo.

A

Usually a mixture of both Sn1 and Sn2.

53
Q

State the product and catalyst of an alkene reacting with water (outline the mechanism).

A

Hydration reaction by the way converts alkene into alcohol.

Concentrated sulfuric acid as a catalyst
also heat with steam.

Involves an intermediate in which both H+ and HSO4- ions are added across the double bond, followed by hydrolysis with replacement of HSO4- by OH- and thus reformation of the H2SO4.

54
Q

State the hybridization, shape and angle and thus a consequence of the carbon atoms in double bonds.

A

sp2
planar triangular shape
120 angle

Fairly open structure, ease for incoming groups to attack.

55
Q

Determine the trend of the rate of nucleophilic substitution reactions in group 17.

A

Increases down group 17 from fluoroalkane to iodoalkane.

56
Q

State the product of an. alkene reacting with a halogen

A

dihalogeno compounds

loss of colour

57
Q

Define the hydrogenation of alkenes.

A

In the presence of a catalyst (Ni, Pa) and under high temperature the formation of alkanes from alkenes.

58
Q

Define an electrophile.

A

Electron-deficient species forming a bond by accepting the electron pair.

Will have partial positive charge or be a positive ion.

59
Q

Define why the Sn2 reaction is stereospecific.

A

Because the three-dimensional arrangements of the reactants determines the three-dimensional configuration of the products.

Because bond formation comes before the bond cleavage in the transition state and so the stereochemistry of the attacked carbon is not lost.

60
Q

State the solvent preferred in Sn1 reactions.

A

Polar protic solvents.

61
Q

State the functional group and it’s name, the suffix and a general formula of alkanes.

A

-ane
CnH2n+2

62
Q

State the functional group and it’s name, the suffix and a general formula of alkenes.

A
  • C=C
  • alkenyl
    -ene
    -CnH2n
63
Q

State the functional group and it’s name, the suffix and a general formula of alkynes.

A

C(triple bond)C
- alkynyl
-yne
CnH2n-2

64
Q

State the functional group and it’s name, the suffix and a general formula of alcholos.

A

-OH
hydroxyl
-anol
CnH2n+1OH

65
Q

State the functional group and it’s name, the suffix and a general formula of aldehydes.

A

-C-H=O
aldehyde, carbonyl
-anal
R-CHO

66
Q

State the functional group and it’s name, the suffix and a general formula of carboxylic acids.

A

=O-C-O-H
carboxyl
-anoic acid
CnH2n+1COOH

67
Q

State the functional group and it’s name, the suffix and a general formula of nitriles.

A

-C(triplebond)N
nitrile
-anenitrile

68
Q

State the functional group and it’s name, the suffix and a general formula of amines.

A

-NH2
amine
-anamine

69
Q

Define a homologous series.

A

Compounds that differ by “-CH2” consecutively and have the same functional group.

70
Q

Define a functional group.

A

Group of atoms that will influence the properties of a compound and its reactivity
usually contains a heteroatom -> different than H or C.

71
Q

List the main features of a homologous series.

A
  • successive members differ by -CH2- group
  • members can be represented by the same general formula
  • members show a gradation in their physical properties
  • members have similar chemical properties
72
Q

List and distinguish the types of drawing of organic compounds.

A
  • full structural formula - shows every bond and atom
  • condensed structural formula - omits bonds where they can be assumed and groups atoms together.
  • stereochemical formula - attempts to show the relative position of atoms and groups around carbon in three dimensions.
73
Q

List the steps of correctly naming a compound according to IUPAC.

A
  1. identify the longest straight chain of carbon atoms.
  2. identify the functional group and it’s corresponding suffix.
  3. identify the side chains or substituent groups and their prefixes (arrange alphabetically).
74
Q

Recite the homologous series of alkanes.

A

methane
ethane
propane
butane
pentane
hexane
heptane
octane
nonane
decane

75
Q
A