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HUBS191 > CHEM191 Module 3 > Flashcards

CHEM191 Module 3 Flashcards

1
Q

What does Valence shell electron repulsion theory state (VSEPR)?

A

Electrons repel each other maximally, meaning that they will move as far away from one another as possible in the valence shell

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2
Q

Rules of lewis diagrams

A
  • electrons are always found in pairs, to represent orbitals
  • non bonding pairs are represented by two dots
  • Bonds are are represented by two dots or a dash
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3
Q

In lewis diagrams, if there are no more electrons available, but not all atoms have a full valence shell, what happens

A

Need to add double or triple bonds

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4
Q

In lewis diagrams, if there are more electrons available, but all atoms have a full valence shell, what happens

A

Apple to expanded octet rule.
This means that some atoms can take more than 8 electrons in the their valence shell. These include P, S, Cl, As, Se, and Br.

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5
Q

What are hybrid orbitals

A

hybrid orbitals are orbitals between s and p subshells that all electrons can be at to have the same energy/be at the same energy level. Hybrid orbitals have less energy than p orbitals but more that s orbitals

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6
Q

What are sigma bonds

A

Sigma bonds are bonds between only s subshells.

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7
Q

What do organic functional groups alter?

A

They alter the properties of chemicals e.g. Acidity, temperature, and reactivity

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8
Q

Name the functional group
R-OH

A

Alcohol

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9
Q

Name the functional group
R-X

A

Halocarbon
(the x represents any halogen)

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10
Q

Name the functional group
R-O-R

A

Ether

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11
Q

Name the functional group
R-CO-H

A

aldehyde

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12
Q

Name the functional group
R-CO-R

A

Ketone

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13
Q

Name the functional group
R-CO-OH

A

Organic acid

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14
Q

Name the functional group
R-CO-O-R

A

Ester

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15
Q

Name the functional group
R
R-N-R

A

Amine

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16
Q

Name the functional group
R-CO-NH-R

A

Amide

17
Q

What are isomers

A

Molecules with the same molecular formula but different arrangement of atoms

18
Q

What are constitutive isomers

A

Compounds with the same molecular formula but different connections between atoms

19
Q

What are stereoisomers

A

Isomers with the same connections between atoms but orientated differently

20
Q

What are enantiomers

A

Stereoisomers that are mirror images of each other.
To be enantiomer, the molecule must have 4 different groups/atoms attached to it.
Enantiomers have the exact same properties, but have a different optical rotation of polarised light.

21
Q

Difference between and cis and trans isomer

A

Cis isomer has the two X’s on the same side
Trans issuers have the two X’s on different sides

22
Q

Rules of preferred groups

A

Priority is based on atomic number
- higher atomic number = higher the
priority

23
Q

What is the name for an equal mix of both mirror side of enantiomers. And what does and equal amount of both enantiomer mean in terms of light rotation.

A

A racemate or a racemic mixture.
An equal mix of both enantiomers mean that the optical rotation cancels out. This is labelled as (±) a it rotates equally.

24
Q

What are substitution reactions

A

Reactions of organic chemistry that occur via the movement of electrons, which can be drawn via diagrams

25
Q

Heterolytic bond cleavage

A

Both electrons from a bond leave in the same direction

26
Q

What is the problem with bonds if one atom in the bond is highly electronegative?

A

It polarises the bond, the makes it weaker and more likely to break.
The electronegative halogen also makes the carbon that it is attached to, slightly positive (electrophilic), attracting nucleophiles, and the carbon and nucleophile, go and form a new bond.

27
Q

How does an SN1 substitution reaction work?

A

If an atom is significantly more electronegative than the other atom in the bond, it can accept both electrons from the bond. This makes it a good leaving group.
Because if this it will leave to become a negative ion, leaving behind a positive ion. If this Is a carbon it is called a carbocation. The carbon is then vulnerable to nucleophilic attack.

28
Q

What is the transition state for an SN1 substitution reaction?
And what is the reaction intermediate?

A

The half broken bond in the transition state for this reaction.
The carbocation is the reaction intermediate for this reaction as it is so reactive that it doesn’t appear in solution.

29
Q

How does an SN2 substitution reaction work

A

If an atom is only slightly more electronegative than the other, it is a poor leaving group and needs help.
A nucleophile must get close to the delta positive to stabilise the carbon, this allows the leaving group to leave.

30
Q

What is the rate for the SN2 substitution reaction?
And how do I find out if it is 1st order or 0th order?

A

rate = k[Nu:][RC-X]
And if the concentration of nucleophile is increased, and the rate doesn’t change, the reaction is 1st order, and is therefore an SN2 reaction.
If the rate dose change when the concentration of nucleophiles is increase, the reaction is 0th order.

31
Q

What is the reaction rate for SN1?
And is tit 1st or 0th order?

A

rate = k[RC-X]
And the reaction is first order

32
Q

Influences on SN1 and SN2 reactions

A

Attached alkyl groups
-Steric hindrance
-Charge stabilisation
Leaving group

33
Q

What is steric hindrance?

A

If the carbon in the bond is bonded top the other alkyl groups. They will prevent the nucleophile from gaining access.
Because of this, bonded alkyl groups favour SN1 reactions

34
Q

What is charge stabilisation?

A

More alkyl groups bonded to the carbon may partially donate their electrons to the central carbon, this reduces the attraction between the carbon and the leaving group, making it more likely to leave, and therefore favouring the SN1 reaction.

35
Q

What do good and bad leaving groups favour between SN1 and SN2 reactions?

A

Good leaving groups favour SN1 reactions
Poor leaving groups favour SN2 reactions as the leaving group is less likely to leave on its own, and SN1 reactions require the leaving group to leave on its own before the nucleophile can bond to the C.

HUBS191 (11 decks)

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