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Chemistry 3AB > Chapter 12 - Organic Chemistey 2 Functional Groups > Flashcards

Chapter 12 - Organic Chemistey 2 Functional Groups Flashcards

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0
Q

What ability does the presence of functional groups in a molecule have?

A

The predictive ability of the types of reactions the molecule will undergo.

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1
Q

What is a functional group?

A

It is an atom or a group of atoms that determines the chemical and, in part, physical properties of an organic compound.

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2
Q

List some if the functional groups of simple molecules.

A
  • alcohol
  • aldehyde
  • carboxylix acid
  • ketone
  • amine
  • ester
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3
Q

What are some of the chemistry of functional groups related to?

A

The changing oxidation number of the carbon atom that is a part of the group.

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4
Q

What is the functional group present on an alcohol?

A

It is the -OH group attached to a tetrahedral carbon atom.

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5
Q

What are the physical properties of simple alcohols? (Up to 8 carbon atoms)

A

• Colorless liquids at room temperature.

• Boiling point of an alcohol is higher than that of the parent Alkane.
-This is due to the presence of hydrogen bonds as well as dispersion forces between the alcohol molecules, compared to only dispersion forces holding the Alkane molecules together.

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6
Q

List the boiling points of some alcohol.

A
  1. Methanol 65
  2. Ethanol 78
  3. Propan-1-ol 97
  4. Butan-1-ol 118
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7
Q

When do hydrogen bonding occur?

A

It occurs between molecules where a hydrogen atom is bonded to one of the 3 highly electronegative atoms - nitrogen, oxygen or fluorine.

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8
Q

Can hydrogen bonding occur with Alkanes?

A
  • No because there are only carbon and hydrogen atoms.

* Only dispersion forces can exist between Alkane molecules.

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9
Q

Why do alcohols have a much higher melting and boiling points than parent Alkanes?

A

This is because hydrogen bonds are stronger than dispersion forces, and because there will be dispersion forces present in the Alkanes as well.

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10
Q

When does the strength of dispersion forces increase?

A
  • They increases with the increasing number of electrons in the molecule.
  • The alcohol molecule with larger molecular masses have more atoms present in the molecule and so have more electrons.
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11
Q

When does the solubility of alcohol in water decreases?

A
  • When the molecular mass increases. Alcohols with smaller molecular masses are soluble in water.
  • After butanol, the alcohols are essentially insoluble in water.
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12
Q

Why can’t longer chains of alcohol be broken down?

A

This is because the small number of hydrogen bonds that form between the alcohol functional group on he alcohol and surrounding water molecule is not sufficient to make up for the bonds that have to be broken between water molecules.

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13
Q

List the type d Alcohols.

A
  1. Primary Alcohol - one carbon atom and two hydrogen atoms are attached to the carbon atom to which the -OH group is bonded.
  2. Secondary Alcohol - two carbon atoms and one hydrogen atom are attached to the carbon atom to which the -OH group is bonded.
  3. Tertiary Alcohol - three carbon atoms and no hydrogen atoms are attached to the carbon atom to which the -OH group is bonded.
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14
Q

Which alcohols are the most reactive?

A
  1. Primary
  2. Secondary
  3. Tertiary
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15
Q

What happens when the hydrocarbon chain of the alcohol increases in length?

A

The reactivity of the alcohol decreases as the likelihood of a successful collision between the alcohol functional group and the metal is reduced.

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16
Q

What are the two most common reactions of alcohols?

A

Oxidation and Reduction which forms another group of compounds called esters.

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17
Q

How can aldehydes be formed?

A

By the oxidation of primary alcohols.

18
Q

What does the oxidation of primary alcohols to aldehydes involve?

A

It involves the reactions of the alcohol with an oxidizing agent such as an acidified solution of potassium dichromate or an acidified solution of potassium permanganate with the aldehyde being carefully removed (often by distillation) from the reaction mixture as it is formed.

19
Q

How is a carboxylic acid form?

A
  • When an aldehyde is not removed after it is formed, it will react further to produce a compound containing another functional group which is the carboxylic acid group.
  • Carboxylic acids are prepared by the oxidation of primary alcohols or aldehydes, using acidified dichromate or permanganate solutions.
20
Q

How to ensure that the oxidation of a primary alcohol forms a Carboxylic Acid and not an Aldehyde ?

A

The reaction mixture is normally heated for some time, for eg. 30 minutes.

•The oxidation of methanol, and methanol, often leads to the formation of carbon dioxide, rather than methanoic acid, when these conditions are used.

21
Q

Why do carboxylic acids only partially ionize?

A
  • Because they are weak acids.

* Generally, the acid strength decreases with increasing length of the carbon chain.

22
Q

Why do carboxylic acids tend to have a higher melting and boiling point?

A
  • Hydrogen bonds formed between carboxylic acid molecules.
  • The formation of dimers (combinations of two molecules joined together)
  • Also, in general, each carboxylic acid can form hydrogen bonds ‘through’ two of its atoms.
23
Q

Why is it not possible for secondary alcohols to be oxidized to form an aldehyde or carboxylic acid?

A

Because in secondary alcohols, the -OH functional group is not on a terminal or end carbon atom.

24
Q

What does the oxidation of secondary alcohols produce?

A

Under the same conditions as those used for primary alcohols it produces a new functional group - the ketone group.

25
Q

How is a ketone formed?

A

Ketones are formed from the oxidation of secondary alcohols, using acidified dichromate or permanganate solutions.

26
Q

Will tertiary alcohols undergo any oxidation?

A

No.

27
Q

Summaries the oxidation of alcohols.

A

Oxidant: Acidified dichromate / Acidified permanganate solution

  • Primary -> mild conditions produce the aldehyde (RCHO), which can be distilled from the reaction mixture. After heating for a period of time, the carboxylic acid (RCOOH) is produced.
  • Secondary -> formation of the ketone (RCOR’)
  • Tertiary -> No reaction.
28
Q

How do Early Breathalyzers work?

A
  • It consisted of a tube packed with orange potassium dichromate granules and a plastic bag at the end.
  • As the suspect breathed through the tube to fill up the bag, if there was ethanol in the breath, the orange crystals would change to a green colour of chromium (III) ions.
  • If the amount of green colour formed exceeded a particular distance along the tube then the person was considered to have a sufficiently high reading to warrant a more accurate blood alcohol test being performed.
29
Q

Can alcohols undergo oxidation when they are burnt in air or oxygen?

A

Yes, the products of the reaction of an alcohol with excess air are carbon dioxide and water.

30
Q

How are Esters formed?

A

Esters are formed in the reaction between a carboxylic acid and an alcohol in the presence of an acid catalyst such as concentrated sulfuric acid.

31
Q

What happens during the formation of an ester?

A
  • The mixture is normally heated for some time, during which a condensation reactions takes place.
  • Such reactions involve the elimination of a water molecule as the acid combines with the alcohol.
  • In this reaction, the hydrogen from the alcohol group combines with the OH from the carboxylic acid to form water.
32
Q

What is hydrolysis?

A

The reverse of the esterification.

33
Q

How does Hydrolysis occur? (Esters converted back to the original carboxylic acid and alcohol)

A
  • When the esters are reacted with an acid, usually with warming.
  • Warming the ester with a solution of sodium hydroxide (or similar base) can also result in the hydrolysis of the ester.
  • In this case the products of the reaction are the alcohol and the salt of the carboxylic acid.
34
Q

How are amines related to ammonia ?

A
  • structure
  • polar molecules
  • capable of hydrogen bonding to one another and other polar molecules containing oxygen, nitrogen and fluorine.
  • pungent smell; particularly those of lower molecular mass that are more volatile.
  • weak base.
35
Q

Why are the hydrogen bonding interaction between amines weaker than that between alcohols?

A

Because the electronegativity difference between nitrogen and hydrogen is less than that between oxygen and hydrogen.

36
Q

Why do amines have a lower boiling point than alcohols?

A

This is due to the Weaker hydrogen bonding.

37
Q

Why do amines with lower molecular masses usually more soluble in water?

A

This is due to their ability to hydrogen bond to the abundant water molecules.

Increase in molecular mass = decrease in solubility.

38
Q

Why are many prescribed drugs amine?

A
  • Because they are often insoluble in water, getting them into body fluids such as blood plasma is difficult.
  • However, by making use of the basic properties of the amine, the molecule can be converted to a soluble salt by reaction of the amine with an acid such as Hydrochloric acid.
39
Q

What died the name “amino acid” suggests?

A

That these compounds contain an amine and a carboxylic acid functional group.

40
Q

What does the alpha sign stand for?

A

It is used to show that the two functional groups are attached to the same, terminal carbon atom.

41
Q

What does amphoteric mean?

A
  • When a chemical can behave as either an acid or a base.

* This occurs in alpha amino acids as they have both and acidic and a basic functional group.

42
Q

What is a Zwitterion?

A
  • When compounds have a positive charge on one atom and a negative charge on another.
  • There are no un-ionized alpha amino acids.
  • This characteristic of all amino acids means that not only are they amphoteric but they are also buffers.

Chemistry 3AB (8 decks)

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