Significance and natural sources
The life of modern society is impossible to imagine without hydrocarbons. Their primary and main sources in nature are oil and natural gas. Access to the deposits of these minerals and the volume of their reserves are not just a matter of economics. They directly determine the level of well-being of entire states and often become the root cause of large-scale international crises.
Globally, hydrocarbons perform two fundamental functions:
- Energy sources. They are burned as fuel for heating homes and power absolutely all types of modern transport—from ground vehicles to marine vessels and aviation.
- Industrial feedstock. Based on them, the chemical industry synthesizes a colossal amount of products, including modern packaging materials and various household chemicals.
Representatives and their physical properties
The properties of hydrocarbons are extremely diverse and depend on their composition. In everyday life, we regularly encounter various representatives of this class of substances in different states of matter:
- Gases (under normal conditions):
- Methane and propane form the basis of fuel for conventional household gas stoves. At the same time, their delivery methods differ: methane is supplied to consumers via pipeline networks, while propane is traditionally stored and transported in special red-painted gas cylinders.
- Isobutane is also a gas under standard conditions. However, upon increasing pressure, it easily transitions into a liquid state. This exact process is observed when looking at the transparent body of a common lighter, inside of which liquefied isobutane sloshes.
- Liquid mixtures:
- Petroleum refining products are not individual substances. They are complex mixtures of various hydrocarbons. Classic examples of such mixtures are the well-known gasoline, kerosene, and diesel fuel.
- Heavy hydrocarbons:
- The more atoms in a molecule, the denser the substance. Heavy representatives include semi-liquid petroleum jelly and completely solid paraffin.
- It is also worth mentioning naphthalene, a solid cyclic substance long used in everyday life as an effective agent to protect fur and woolen items from clothes moths.
Classification and homologous series
All hydrocarbons are classified according to their structure (presence of cycles) and composition (type of chemical bonds between carbon atoms). Several main homologous series are distinguished.
| Series name | General formula | First representative | Structural features |
|---|---|---|---|
| Alkanes (saturated) | $C_nH_{2n+2}$ | Methane ($CH_4$) | Form zigzag chains that can have branching. |
| Cycloalkanes | $C_nH_{2n}$ | Cyclopropane ($C_3H_6$) | Carbon atoms are closed in rings (cycles). |
| Alkenes | $C_nH_{2n}$ | Ethylene ($C_2H_4$) | Refer to unsaturated hydrocarbons, containing one $C=C$ double bond. |
| Alkynes | $C_nH_{2n-2}$ | Acetylene ($C_2H_2$) | Unsaturated, possessing one $C \equiv C$ triple bond in their structure. |
| Conjugated alkadienes | $C_nH_{2n-2}$ | Butadiene ($C_4H_6$) | Contain strictly two double bonds separated by a single bond: $C=C-C=C$. |
| Arenes | $C_nH_{2n-6}$ | Benzene ($C_6H_6$) | Cyclic conjugated aromatic systems. The basis is a six-membered cycle with (formally) three double bonds. |
Briefly: answers to topical questions
What heavy hydrocarbons are used in medical practice as ointment bases?
Petrolatum and paraffin are used as heavy hydrocarbons in medicine, though their specific use as ointment bases is not described in the sources.
- Petrolatum is a semi-liquid heavy hydrocarbon.
- Paraffin is a solid heavy hydrocarbon.
Liquid paraffin (mineral oil) is used in pediatrics as a softening laxative (emollient) for treating constipation. Additionally, mineral oil and paraffin are used in microbiology to create anaerobic conditions during bacterial cultivation (e.g., nutrient medium overlay or Fortner's method).
Which cycloalkanes exhibit inhalation anesthetic action?
In the cited sources, cyclopropane is listed among general anesthetics whose use is inexpedient. Especially during manipulations on the oropharynx and larynx, its use sharply increases the risk of reflex laryngospasm or bronchospasm, as it increases the reflex excitability of the upper respiratory tract mucosa.
What is the biological role of conjugated diene hydrocarbons (isoprenoids)?
Sources indicate the following information regarding isoprenoids and related compounds:
- Terpenes are substances based on isoprene; they include carotenoids and chlorophyll.
- Ubiquinone contains a long polyunsaturated chain of repeating isoprenoid units; the isoprene group typically repeats 10 times.
- A similar chain is found in the structure of vitamin K group members, vitamin A, and other carotenoids; in vitamins K₂, it repeats 6–9 times.
- Vitamins K act as coenzymes in the carboxylation of glutamyl radicals during the post-translational modification of a number of proteins.
What types of toxic action do aromatic hydrocarbons exert on the human body?
Polycyclic aromatic hydrocarbons (PAHs) exhibit pronounced carcinogenic and mutagenic effects even at extremely low concentrations (fractions of a milligram and micrograms). They cause skin cancer, upper respiratory tract cancer, and lung cancer. An indicator PAH is benz[a]pyrene; it is present in all contaminated environmental objects and possesses clearly expressed carcinogenicity and mutagenicity.
Class and exam questions
How to visually distinguish propane cylinders?
Cylinders used for storing and transporting propane are traditionally painted red.
Is gasoline a single specific chemical substance?
No, gasoline, just like kerosene or diesel fuel, is a petroleum refining product and represents a complex mixture of hydrocarbons of varying composition.
What else to study on this topic
- Spatial structure of alkane zigzag chains
- Specificity of conjugation in the butadiene molecule
- Features of the benzene aromatic ring (why double bonds are considered formal)
- Differences in oil refining processes for the production of gasoline and petroleum jelly
Master the entire topic in the "Chemistry" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on the topic «Hydrocarbons» and 3,009 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 95 video lessons for the subject
Other topics in "Chapter 15. Hydrocarbons"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.