Chem - Chapter 12 - Organic Chemistry 2 : Functional Groups

What are the 3 types of alcohols? What is this based on?

1. Primary - 1º 2. Secondary - 2º 3. Tertiary - 3º This classification is based on the number of carbon atoms are attached to the carbon atoms to which the -OH group is bonded.

Explain how alpha-amino acids behave in solutions of different pH's

At high pH values (basic solutions), the carboxylic acid functional group donates its hydrogen ion to produce the carboxylate ion functional group, -COO⁻. At low pH values (acidic solution), the amine functional group accepts a hydrogen to become NH₃⁺. Because acids donate H⁺ and bases accept H⁺

What do alcohols form when they undergo oxidation when burnt in air or oxygen?

Carbon dioxide and water in EXCESS air or oxygen.

Do tertiary alcohols undergo oxidation?

No

What is the functional group present in an alcohol?

The -OH group attached to a tetrahedral carbon atom.

What is the functional group for primary amines? And what is it's suffix?

- NH₂, where the nitrogen is bonded directly to a carbon atom. The suffix 'amine' is used instead of the 'e' of the parent alkane and a number is used to show it's position in the chain.

What are the physical properties of alcohols?

1. The simple alcohols with up to eight carbon atoms in the longer chains are colourless liquids at room temperature 2. The boiling and melting points of an alcohol is higher than that of the parent alkane 3. As molecular mass of alcohols increase, so does their solubility in water. After butanol, the alcohols are essentially insoluble.

What are some properties of primary amines?

1. They are capable of hydrogen bonding 2. They have much higher boiling and melting points compared to their parent chain, but lower than alcohols with similar molecular masses 3. They are soluble in water when they have shorter hydrocarbon chains 4. They have a pungent smell like ammonia 5. They are weak bases

What are some properties of carboxylic acids?

1. They are weak acids 2. The acid strength generally decreasing with increasing length of the carbon chain 3. They react with bases 4. They are soluble in water with up to 4 carbons in a chain 5. They tend to have higher melting and boiling points compared to other organic molecules of similar molecule mass

What type of reaction occurs to form an ester? Why?

A condensation reaction takes places because there is the elimination of a water molecules as the acid combines with the alcohol.

What is a functional group?

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

What is the product when a secondary alcohol is oxidised?

A ketone is formed.

What is produced when a primary alcohol is oxidised?

A primary alcohol can be oxidised to form a compound containing the aldehyde functional group or the carboxylic functional group, depending on the experimental conditions used for the oxidation.

Why is the classification of alcohols as primary, secondary and tertiary important?

Because each of these types of alcohol behaves in a different fashion chemically.

Why do carboxylic acids tend to have higher melting and boiling points compared to other organic molecules of similar molecular masses?

Because hydrogen bonds form between carboxylic acid molecules in two of their atoms and they form dimers (combinations of two molecules joined together), in the pure liquid.

Why are carboxylic acids soluble in water?

Because of the hydrogen bonding that exists between the acid molecules and the water molecules. Because each carboxylic acid has both an -OH group and another polar oxygen atom to form hydrogen bonds with water molecules, these acids are more soluble in water than alcohols of similar mass.

Why aren't carboxylic acids with longer chains soluble in water?

Because the effect of the non-polar hydrocarbon chain starts to dominate and it's polarity and hydrogen bond strength becomes negligible.

Why are alpha-amino acids amphoteric?

Because they an both an acidic and a basic functional group, therefore they can behave as either an acid or base.

Why are amino acids highly soluble in water?

Because they have an alcohol group they exhibit hydrogen bonding and therefore are able to break the bonds between water molecules and have enough energy to form new ones, hence be soluble in water.

What else are alpha-amino acids used as? Why?

Buffers, because they can act as an acid or base to maintain pH.

What is the functional group for a carboxylic acid and what is it's suffix?

Carboxylic acids contain the functional group -COOH. The suffix used is 'oic acid' in the place of the 'e' in the name of the parent alkane.

What are alpha- amino acids?

Compounds that contain an amine and a carboxylic functional group. The alpha is used to show that the two functional groups are attached to the same, terminal carbon atom.

What happens when you warm the ester with a solution base?

Hydrolysis occurs, but the products of the reaction are the alcohol and the salt of the carboxylic acid.

How are esters formed?

In the reactions between a carboxylic acid and an alcohol.

Explain the trend between the reactivity of the alcohol and the metal as the hydrocarbon chain of the alcohol increases. Why?

It decrease, because the likelihood of a successful collision between the alcohol functioning group and the metal is reduced.

What is the functional group for an aldehyde and what is it's suffix?

It's function group is -CHO, where a double bond exists between the C and O. Aldehydes are named using the suffice 'al'

What is the functional group of a ketone and what is it suffix?

Ketones are names by replacing the 'e' in the alkane chain with 'one'

Can ketones be oxidised any further?

No.

What is the order of reactivity for alcohols with comparable molecular masses?

Primary>Secondary>Tertiary

What is the general equation of a reaction between an alcohol and a reactive metal?

R-OH(l) + Metal(s) → Metal⁺ + H₂(g) + R-O⁻ An alcohol plus a solid metal forms the metal ions, hydrogen gas and the alcohol ion without the H⁺ on the functional group.

What type of reaction occurs when aldehydes are formed through oxidation of primary alcohols?

Redox reactions.

Explain how carboxylic acids are formed through oxidation of primary alcohols.

The aldehyde functional group can be further oxidised under the same conditions as the oxidation of the primary alcohol to produced a carboxylic acid.

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

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

How is water and an ester formed through the reaction between an alcohol and a carboxylic acid?

The hydrogen from the alcohol group combines with the OH from the carboxylic acid to form water and the oxygen on the alcohol bonds with the CO carbon atom to form the ester functional group.

How are esters named?

The name of an ester comprises of two words. The first word is the alkyl group from the alcohol that reacts, and the last work is derived from the carboxylic acid by replacing the 'ic acid' with 'ate'

Explain how aldehydes are formed through oxidation of primary alcohols.

The oxidation of primary alcohols to aldehydes involves the reaction of the alcohol with an oxidising 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.

What are functional groups important in determining?

The presence of a particular functional group in a molecules can be used to predict the type of reactions the molecule will undergo. This predictive ability is very important in the synthesis of new organic molecules.

What is required in the reaction to form an ester?

The presence of an acid catalyst such as concentrates sulfuric acid is needed. The mixture is normally heated for some time.

What condition is required to ensure that the carboxylic acid is formed rather than the aldehyde?

The reaction mixture is normally heated, for example, 30 minutes.

How can esters be concerted back to the original carboxylic acid and alcohol?

The reverse of the esterification reaction is called hydrolysis, when the ester is reacted with an acid and warming.

What is meant by 'alpha-amino acids are zwitterion's'?

There are no un-ionised alpha-amino acids, in the solid and aqueous state, they do not have the amine and carboxylic acid groups present as -NH₂ and -COOH, but rather their ionic forms, NH₃⁺ and COO⁻.

Where are esters found?

They occur naturally in many fruits and are responsible for the 'fruity odour' of many fruits. They are also present in fats and vegetable oils. Commercially, esters are used to make food flavours, perfumes, scents, industrial solvents, and as softening agents in the plastics industry.

Why are smaller alcohol molecules soluble in water, but after butanol essentially insoluble?

This is because smaller alcohol molecules have hydrogen bonding similar in strength between the water molecules, therefore have sufficient energy to break and create new bonds. However, for larger molecules if they were to dissolve, the larger hydrocarbon chain would need to push many water molecules apart, thereby breaking the hydrogen bonds between the water molecules. However, the small number of hydrogen bonds that form between the alcohol functional group on the alcohol and surrounding molecules don't create enough energy to make up for the bonds that have to be broken between water molecules.

Why is there a gradual increase in boiling points of the alcohols as successive -CH₂- groups are added?

This is due to the increasing strength of the dispersion forces. The hydrogen bonding interaction will be the same for all the alcohols as they only contain one alcohol functioning group. However, the strength of dispersion forces increases with increasing number of electrons in the molecules. The alcohol molecules with larger molecular masses have more atoms present int he molecule and so have more electrons.

Why are the boiling and melting points of alcohols higher than their parent alkane's?

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.

Are ketones soluble in water?

Yes, because the oxygen atom in the ketone is capable of hydrogen bonding with the hydrogen atom in water, however as the carbon chains increases in length the solubility of the ketone decreases.

Can alcohols exhibit structural isomerism?

Yes, the same molecular formula can be any type of alcohol, depending on the number of each atom.

Is an amine still an amine if it's carbon atom it's bonded to is bonded to two other carbons?

Yes.

What are some properties of amino acids?

∙ At room temperature, amino acids are all solids with relatively high melting and boiling points, like ionic compounds. ∙ They are relatively soluble in water

What is primary, secondary and tertiary alcohols?

∙ Primary alcohols are those in which one carbon atom is attached to the carbon atoms to which the -OH group is bonded. ∙ Secondary alcohols are those in which two carbon atoms are attached to the carbon atoms to which the -OH group is bonded. ∙ Tertiary alcohols are those in which three carbon atoms are attached to the carbon atoms to which the -OH group is bonded.

What are the reactions of alcohols?

∙ Reactions with reactive metals ∙ Oxidation of alcohols, to form: ◇ Aldehydes ◇ Carboxylic Acids ◇ Ketones ∙ Reaction with carboxylic acid to form an ester