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1.2 Organic Chemistry > Definitions > Flashcards

Definitions Flashcards

1
Q

Define an enantiomer

1 of 3 definitions

A

Either of a pair of chemical compounds whose molecular structures have a mirror-image relationship to each other

One of two stereoisomers that are mirror images of each other that are non-superposable

non-superimposable mirror-image structures

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2
Q

Define a nucleophile

A

A chemical species with an electron rich atom that is capable of donating a pair of electrons

Lewis basis (proton donator or electron pair donator)

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3
Q

Define an electrophile

A

A chemical species with an electron deficient atom that is capable of accepting a pair of electrons

Lewis acids (proton acceptor or electron pair acceptor)

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4
Q

Define a primary alcohol

A

An alcohol with 1 carbon directly attached to the C-OH functional group

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5
Q

Define a secondary alcohol

A

An alcohol with 2 carbons directly attached to the C-OH functional group

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6
Q

Define a tertiary alcohol

A

An alcohol with 3 carbons directly attached to the C-OH

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7
Q

Define ragiochemistry.

A

Regiochemistry refers to how certain reactions end up forming one constitutional isomer over another

Regioisomers result (different products)

Ragioselective - reaction has a preference for forming one regioisomer over another.

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8
Q

What is a pair of non-superimposable mirror-image structures called?

A

An enantiomer

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9
Q

What is a heteroatom?

A

Any atom other than C and H in organic chemistry

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10
Q

What are SN1 and SN2 reactions ?

A

Nucelophilic substitution reactions

1 = unimolecular (substrate only)
2 = biomolecular (substrate and nucleophile)
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11
Q

Write a note on how an SN1 reaction occurs.

2

A

The SN1 reaction proceeds stepwise.

The leaving group is removed which forms the carbocation

Carbocation is attacked by the nucleophile.

The deprotonation of the protonated nucleophile takes place to give the required product

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12
Q

Write a note on how SN2 reactions occur.

A

SN2 occurs in one step, one bond is broken and one bond is formed in the same step

The nucleophile approaches the carbon atom to which the leaving group is attached.

As the nucleophile forms a bond with this carbon atom, the bond between the carbon atom and the leaving group breaks.

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13
Q

What can prevent SN2 reactions?

A

steric hindrance.

The reaction will only proceed if the empty orbital is accessible.

The more groups that are present around the vicinity of the leaving group (alkyl halides), the slower the reaction will be.

That’s why the rate of reaction proceeds from primary (fastest) > secondary&raquo_space; tertiary (slowest)

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14
Q

What can prevent SN1 reactions

A

Carbocation stability

Since the first step of the SN1 reaction is loss of a leaving group to give a carbocation, the rate of the reaction will be proportional to the stability of the carbocation.

Carbocation stability increases with increasing substitution of the carbon (tertiary > secondary&raquo_space; primary) as well as with resonance.

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15
Q

Differences between SN1 and SN2

3 +3

A

SN1

  • rate of reaction is unimolecular
  • two step mechanism
  • carbocation formed as intermediate

SN2

  • rate of reaction is bimolecular
  • 1 step mechanism
  • carbocation not formed as intermediate
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16
Q

Define isomers

A

Each of two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.

17
Q

Define chain isomerism

A

Different arrangements of carbon atoms leading to linear and branched chains

18
Q

Define structural/constitutional isomers.

A

Are compounds with the same molecular formula

but different structural formulas

19
Q

Define positional isomerism.

A

In position isomerism, the basic C skeleton remains unchanged but important groups are
moved around on that skeleton

20
Q

Define functional group isomerism.

A

isomers contain different functional groups,

that is, they belong to different families of compounds (different homologous series

21
Q

Classify isomerism.

A

Structural/constitutional

Sterioisomers

22
Q

What is sterioisomerism?

A

Isomers that comprise the same parts but differ in spatial orientation are termed as stereoisomers

23
Q

What are the two types of sterioisomers?

A

Conformational

Configurational/geometric

24
Q

What is conformational isomerism?

A

a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds (refer to figure on single bond rotation)

25
Q

What is configurational/geometric isomerism?

A

stereoisomers that cannot be converted into one another by rotating the molecule around a single bond

Cis-trans isomerism

26
Q

List the different types of structural/constitutional isomerism.

A

Carbon chain isomerism

Functional group isomerism

Positional isomerism

27
Q

What is an E alkene?

A

A trans alkene

2 of same atom on different sides of double bond

28
Q

What is a Z alkene?

A

A cis alkene

2 of same atoms on same side of double bond

29
Q

Define a dehydrohalogenation reaction.

A

An elimination reaction in which a H and a halogen are removed by a base to form a pi bond

30
Q

Define an addition reaction.

A

A reaction in which 2 or more reactants combine to form products

31
Q

Define tautomerization

A

The process of converting one tautomer into another

Catalysed by both acid and base

32
Q

Define tautomers

A

Constitutional isomers that differ in the location of a double bond and a hydrogen atom

33
Q

What is an enol form?

A

Double bond and Hydrogen run longitudinally parallel to each other

34
Q

What is a keto form?

A

Double bond and hydrogen run latitudinally parallel to each other

35
Q

Define a sigma bond

A

A sigma bond is formed by the head-on overlap of two orbitals

36
Q

Define a pi bond

A

A pi bond is formed by the sideways overlap of p orbitals

37
Q

What are the main differences between pi bonds and sigma bonds?
(5)

A

Sigma = head on overlap, pi = sideways overlap

Sigma = s or p orbitals
Pi = only p orbitals

Sigma determines shape of molecule, pi does not

Sigma is a strong bond, pi is not

Free rotation about sigma, restricted rotation about pi

38
Q

What is a chiral centre?

A

Chiral centre is an asymmetric tetrahedral carbon atom that is bonded with four different groups.

39
Q

What is a leaving group?

2

A

A leaving group is an atom or group of atoms that are able to break away from a molecule with a lone pair, breaking the bond between it and the molecule

It acts as the opposite of a nucleophile; instead of donating electrons to form a covalent bond, it breaks that bond and takes the electrons as it leaves

1.2 Organic Chemistry (15 decks)

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