Hydrocarbon derivatives

Hydrocarbon derivatives are compounds made up of carbon atoms and at least one other

atom that is not hydrogen.

Table 1.11 Common Functional Groups

 

Alcohols

An alcohol is a hydrocarbon derivative that contains a hydroxyl functional group. A

hydroxyl group consists of an oxygen atom and a hydrogen atom (-OH). Alcohols are

components of many commonly used products. Table 1.12 summarizes a few commonalcohols and some of their uses.

Table 1.12 Common Alcohols and Their Uses

 

Haloalkanes

A haloalkane is a hydrocarbon that contains at least one halogen atom. Haloalkanes

are not found in living systems but are artificial. Trichloromethane, commonly known

as chloroform, was once used as an anaesthetic. It is no longer used as such because

it is now considered a possible carcinogen. Another familiar group of haloalkanes,

chlorofluorocarbons (CFCs), were once used as refrigerants and as propellants in spray

cans. In addition to being potent greenhouse gases, CFCs are responsible for damage to the

ozone layer. The ozone layer in the stratosphere normally

absorbs most ultraviolet light before it reaches Earth’s surface. The reduction of the ozone

layer permits dangerous levels of ultraviolet light from the Sun to reach the ground. Because

serious health effects such as skin cancer, as well as crop damage, can result from exposureto ultraviolet light

 

Physical Properties of Haloalkanes

Similar to the alkanes, only the smallest haloalkanes (fluoromethane, chloromethane,

bromomethane, and iodomethane) are slightly soluble in water. All of the other haloalkanes

are insoluble in water. In contrast, the boiling points of the haloalkanes differ greatly from

those of alkanes with the same number of carbon atoms. For example, the boiling point of

methane is -161°C, whereas the boiling point of chloromethane is -24.2°C and that of

iodomethane is 42°C. The boiling point of propane is -42.1°C, whereas that of

1-chloropropane is 45.6°C and that of 1-iodopropane is 102.5°C.

Aldehydes

You may be familiar with the smell of the most common aldehyde, formaldehyde (methanal).

A water solution of formaldehyde, called formalin, is often used to preserve organisms, such

as frogs, for dissection in school laboratories. The federal government and several provincial

governments have placed legal limits on human exposure to formaldehyde. As a result, the

concentration of formaldehyde currently found in laboratories, such as those in Ontario

classrooms, has been deemed safe. Nevertheless, researchers are trying to find alternatives to

formalin because of its toxic effects at high concentrations.

Aldehydes, as well as several other hydrocarbon derivatives discussed later in this

section, contain a carbonyl functional group. A carbonyl group (>C=O) is a functional

group containing a carbon atom that is double bonded to an oxygen atom.

 Carbonyl groups are components of several different

functional groups. In aldehydes, a carbonyl group is part of a larger functional group

that also contains a hydrogen atom bonded to the carbon atom.

By definition, an aldehyde is a hydrocarbon derivative that contains a formyl group.

Notice that three bonds on the carbon atom in the formyl group are bonded to the other

atoms in the group. There is only one position available on the carbon atom to bond to

other atoms. Therefore, this group is always found at the end of a hydrocarbon chain.

Naming and Drawing Aldehydes

Aldehydes are named in much the same way as alcohols are named. That is, the root of the

name of an aldehyde is based on the parent alkane, the alkane having the same basic carbon

structure.

Physical Properties of Aldehydes

The carbonyl group of aldehydes is very polar but the carbon-hydrogen bonds are not.

Thus, aldehydes cannot hydrogen bond with one another but they can hydrogen bond with

water. Therefore, the strength of the attraction among aldehyde molecules is not as strong as

that between alcohol molecules, which can bond with one another.

As a result, the boiling points of aldehydes are lower than those of alcohols having

the same number of carbon atoms. Only methanal (formaldehyde) is a gas at room

temperature. Ethanal has a boiling point of 20.1°C, which is very close to room temperature.

So, it is either a very volatile liquid or a gas, depending on the exact temperature of the

room. Aldehydes from three to 14 carbons long are liquids at room temperature, while

those with carbon chains of 15 carbon atoms or longer are waxy solids.

The small aldehydes having one through four carbon atoms are soluble in water and

those with five through seven carbon atoms are slightly soluble in water. When the carbon

chain gets longer than seven carbon atoms, the insoluble nature of the hydrocarbon chain

overcomes the solubility of the polar carbonyl group and the aldehydes are insoluble in

water. Short chain aldehydes have a very pungent odour but, as the chain gets larger, the

odour becomes more pleasant.

aldehyde and ketones

Ketones

Acetone is the common name for the ketone, propanone. Because it dissolves many

compounds that are insoluble in water, it is used to remove nail polish from fingernails,

ink stains from fingers, as well as price–tag stickers from glass, metal, or porcelain objects.

However, it cannot be used on a plastic surface without dissolving the surface itself.

The smell of acetone may also indicate the presence of a serious health condition.

Breath that smells like acetone can be a sign of a dangerous condition known as diabetic

ketoacidosis. This condition occurs when a diabetic individual is unable to produce enough

insulin to utilize glucose as a fuel source for the body. Instead, the body burns fatty acids.

Ketones, a by–product of fatty acid metabolism, produce the scent of acetone on the breath.

If not treated immediately, diabetic ketoacidosis can cause a diabetic coma and death.

A ketone, like an aldehyde, contains a carbonyl group (>C=O). Unlike aldehydes, the

carbon atom in the carbonyl group of a ketone is bonded to two carbon atoms or carbon

chains.

Naming and Drawing Ketones

Like alcohols and aldehydes, ketones are named according to the parent alkane. Thus, the

root of the name of the ketone is the root of the alkane.

Keep in mind that, to draw ketones, the number in the suffix refers to the

carbon atom in the carbonyl group.

Physical Properties of Ketones

Ketones, like aldehydes, have a carbonyl group that is very polar but have no hydrogen

atoms bonded to strongly electronegative atoms. Thus, they cannot hydrogen bond with

one another. However, they can hydrogen bond with water molecules. As a result, ketones

have boiling points and solubilities similar to those of aldehydes. Like aldehydes, ketones

that have carbon chains of 15 carbon atoms or longer are waxy solids at room temperature.

However, all smaller ketones are liquid at room temperature.

Carboxylic Acids

a carboxylic acid found in vinegar. Similarly, if you eat oranges, you are consuming

another carboxylic acid called 3-carboxy-3-hydroxypentanedioic acid, commonly known as

citric acid. Tamarinds, the fruit of a tamarind tree, contain tartaric acid, another example of

a carboxylic acid.

Esters

When you smell the aroma of fresh fruit such as raspberries, you probably do not think

about what chemical compound might be producing the pleasant fruity odor. In many

cases, the fruity odor is caused by a compound called an ester. An ester is a hydrocarbon

derivative that contains the functional

The general formula for an ester is RCOOR9. The symbol R representsany hydrocarbon

or just a hydrogen atom. The symbol R9 represents a hydrocarbon and, therefore, it must

contain at least one carbon atom. To name an ester, it helps to think of it as a combination

of a carboxylic acid and an alcohol because the names of those compounds are used in the

name of the ester.

Physical Properties of Esters

The presence of the >C=O group makes esters somewhat polar but without an −OH

group, ester molecules cannotform hydrogen bonds with one another. Therefore, the

boiling points are lower than the corresponding alcohols and carboxylic acids. The smaller

esters are liquids at standard temperature while the longer chain esters are waxy solids.

Esters with four or fewer carbon atoms are soluble in water while larger esters are insoluble.

The most noticeable characteristic of esters is their volatility, which allows them to generate

aromas.

Ethers

Before the 1840s, no anaesthetic was available for surgery patients. Very few surgeries were

performed but the few that were done were extremely painful. In 1842, the first surgery

was performed using ether (ethoxyethane or diethyl ether) as an anaesthetic. The field of

surgery was transformed. However, ether is very flammable and causes severe nausea and

vomiting. Doctors searched for other anaesthetics but ether remained in use for many

years. Today, due to its low cost and availability, ether is still sometimes used for surgery in

the developing world. As well, it is still often used in “fly labs” to anaesthetise fruit flies so

genetics students can study their inheritance patterns.

Ether has other, numerous current uses, such as a starter for diesel engines in extremely

cold weather. It is also used as an aerosol propellant, solvent, and plasticiser. One type of

ether, methyl tertiary butyl ether (MTBE), is used as a gasoline additive. Although it helps

gasoline to burn cleaner, spillage and leakage around gas stations have resulted in the

pollution of ground water. Therefore, its use has been greatly decreased.

An ether is a hydrocarbon derivative in which an oxygen atom is single bonded to two

carbon atoms. The functional group can be written as –O–. The general formula for all

ethers can be expressed as R–O–R9, where R and R9 are alkyl groups.

Naming and Drawing Ethers

The IUPAC system of naming ethers identifies the longer carbon chain as the R group. The

R group is designated as the main chain in the molecule and takes the name of the parent

alkane. The oxygen and shorter carbonchain (–O–R9) group make up the side group. This

side group is called an alkoxy group.This group is named by adding -oxy to the root name

of the R9 group. For example, the alkoxy group in CH3–CH2–CH2–O–CH3 is methoxy-.

The main chain is propane.

Physical Properties of Ethers

The bond angle formed by the C–O bonds in ethers,

If the bonds formed a straight line, the two bond dipoles would cancel each

other. Nevertheless, ethers are not as polar as any of the other common hydrocarbon

derivatives you have studied. As well, because ether molecules cannot form hydrogen bonds

with one another, the attraction between them is small. As a result, ethers with a total of

two or three carbon atoms are gases at room temperature while larger ethers are liquids.

Ethers can form hydrogen bonds with water molecules. Thus, ethers with two or three

carbon atoms are soluble in water. Straight chain ethers with a total of four to six carbon

atoms are slightly soluble while all larger ethers are insoluble in water

Amines

You may have noticed that fish dishes are often prepared or served with lemon,This is done to reduce the odour associated with fish. “That fishy odour” is

due to the presence of amines, volatile hydrocarbon derivatives that tend to vapourize. The

citric acid in the lemon juice neutralizes the amines, which are basic molecules. The acid

converts the amines to their salt form, which is not volatile. Thus, lemon juice eliminates

the odour.Amines have other practical uses, such as corrosion inhibitors in boilers, antioxidants

in roofing asphalt, flotation agents in mining, and many more. Amines are also components

of important biological molecules. When you are in a dangerous situation, a complex

amine, adrenaline, is released into your blood. Once in your blood, adrenaline increases

your heartbeat and respiration and helps to release more glucose into your bloodstream. In

this way, it prepares your body for the “fight or flight” response to danger.

An amine is a hydrocarbon derivative that contains a nitrogen atom bonded to at least

one carbon atom, although it may be bonded to up to three. Chemists separate amines into

three categories depending on the number of carbon atoms bonded to the nitrogen atom.

Primary amines have one carbon atom

bonded to the nitrogen, secondary amines have two, and tertiary amines have three.

Naming and Drawing Amines

The IUPAC system of naming amines considers the longer hydrocarbon group bonded to

the nitrogen to be the main chain. Smaller hydrocarbons bonded to the nitrogen are dealt

with as side groups. 

Physical Properties of Amines

The N-H bonds in primary and secondary amines are very polar. However, tertiary amines

do not have N-H bonds. Thus, primary and secondary amines can hydrogen bond with

one another but tertiary amines cannot. Therefore, primary and secondary amines have

relatively high boiling points compared to ethers and alkanes of a similar size. As well, they

have higher boiling points than tertiary amines with the same number of carbon atoms.

carbon atoms. For example, ethanamine, a primary amine, and N-methylmethanamine,

a secondary amine, both have two carbon atoms and their boiling points differ by about

10°C. N,N-dimethylmethanamine, a tertiary amine, and propan-1-amine, a primary amine,

both have three carbon atoms but their boiling points differ by more than 45°C.

All amines can hydrogen bond with water. Therefore, the smaller amines are very

soluble in water.

Amides

Have you ever had a headache and reached for a bottle containing pain reliever tablets?

Unlike Aspirin products, most other pain medications,

Penicillin is also an amide but it is very complex. It

contains several other functional groups in addition to an amide group. Another amide,

commonly called dimethylformamide, is a very commonly used organic solvent in industry.

Most common commercial uses of amides, however, are in polymers such as nylon and

polyacrylamide. Amides are hydrocarbon derivatives containing the functional group, –CON–, which

is a carbonyl group bonded to a nitrogen atom. One, or both, of the hydrogen atoms on

the nitrogen atom can be replaced by alkyl groups. Similar to the case of amines, such

replacements result in secondary and tertiary amides. 

Naming and Drawing Amides

The root of an amide comes from the part of the amide that contains the carbonyl carbon.