Why is carbon special, and how are the hydrocarbon families organized and named?
Organic chemistry and hydrocarbons: classify alkanes, alkenes and alkynes using their general formulas, and name simple hydrocarbons using Table P and Table Q.
A focused Regents Chemistry answer on organic chemistry and hydrocarbons: why carbon forms so many compounds, the alkane, alkene and alkyne homologous series with their general formulas, isomers, and naming using the Table P and Table Q reference data.
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What this topic is asking
The Core Curriculum asks you to recognize that carbon forms a huge variety of compounds, to classify the hydrocarbon families (alkanes, alkenes, alkynes) by their general formulas, to understand isomers, and to name simple hydrocarbons using Table P (carbon-chain prefixes) and Table Q (the homologous series). This is the entry point to organic chemistry on the Regents.
Why carbon is special
Organic compounds are built on carbon skeletons with hydrogen and often oxygen, nitrogen or halogens attached. The Regents focuses on hydrocarbons and a set of functional groups (the next page), keeping naming at a basic level.
The homologous series
Table Q gives the general formula and bonding of each:
- Alkanes (): only single carbon-carbon bonds, so they are saturated (they hold the maximum number of hydrogen atoms). Example: methane , ethane .
- Alkenes (): contain one carbon-carbon double bond, so they are unsaturated. Example: ethene .
- Alkynes (): contain one carbon-carbon triple bond, also unsaturated. Example: ethyne .
Naming simple hydrocarbons
To name a hydrocarbon from its formula: count the carbons to get the prefix from Table P, then use the general formulas on Table Q to decide the series (and so the ending). For , four carbons (but-) and the alkane formula ( with ) give butane.
Isomers
Isomerism is part of why carbon forms so many compounds: a single formula can correspond to more than one structure once the chain has four or more carbons. The Regents asks you to recognize that isomers share a molecular formula but differ in structure.
Try this
Q1. State the general formula of the alkane series. [1 point]
- Cue. (from Table Q).
Q2. Name the straight-chain alkane with four carbon atoms. [1 point]
- Cue. Butane (but- for four carbons, -ane for an alkane).
Exam-style practice questions
Practice questions written in the style of NYSED exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Regents (Part A style)1 marksWhich is the general formula for the alkene series of hydrocarbons? (1) (2) (3) (4) Show worked answer →
A 1-point Part A item on the homologous series. The answer is (2) .
Table Q gives the general formulas: alkanes are (all single bonds, saturated), alkenes are (one double bond), and alkynes are (one triple bond). The alkene formula has two fewer hydrogens than the alkane because of the double bond.
Markers reward selecting for the alkenes, as listed on Table Q.
Regents (Part B-2 style)3 marksA hydrocarbon has the formula . (a) Identify the homologous series it belongs to. (b) State its name using Table P. (c) State whether it is saturated or unsaturated, and explain.Show worked answer →
A 3-point constructed-response item on naming and classifying.
(a) Series (1 point): fits (with , ), so it is an alkane.
(b) Name (1 point): the prefix for three carbons is "prop-" (Table P), and the alkane ending is "-ane", so the name is propane.
(c) Saturated or unsaturated (1 point): it is saturated, because it contains only single carbon-carbon bonds (the maximum number of hydrogen atoms).
Markers reward identifying the alkane series from the formula, naming it with the Table P prefix and the -ane ending, and explaining that single bonds mean it is saturated.
Related dot points
- Organic reactions and functional groups: identify organic classes from their functional groups using Table R, and recognize the main organic reactions such as combustion, substitution, addition, esterification and polymerization.
A focused Regents Chemistry answer on functional groups and organic reactions: identifying alcohols, acids, esters and other classes from Table R, and recognizing combustion, substitution, addition, esterification, saponification, fermentation and polymerization.
- Oxidation numbers and redox reactions: assign oxidation numbers using the standard rules, and identify oxidation, reduction, and the oxidizing and reducing agents in a reaction.
A focused Regents Chemistry answer on oxidation numbers and redox: the rules for assigning oxidation states, the meaning of oxidation (loss of electrons) and reduction (gain of electrons), and how to identify the oxidizing and reducing agents.
- Types of chemical reactions: classify reactions as synthesis, decomposition, single replacement, double replacement or combustion, and use Table J and Table F to predict whether a reaction occurs.
A focused Regents Chemistry answer on classifying reactions as synthesis, decomposition, single replacement, double replacement or combustion, and using the Table J activity series and Table F solubility guidelines to predict products and precipitates.
- Types of chemical bonds: distinguish ionic, covalent and metallic bonding in terms of electron transfer or sharing, and relate bond type to the elements involved.
A focused Regents Chemistry answer on ionic, covalent and metallic bonding: how electrons are transferred or shared, why bonds form to reach stability, the role of energy, and how to predict bond type from the elements involved.
- Nuclear chemistry: identify alpha, beta, positron and gamma radiation, balance nuclear equations, and use half-life with the Table T relationship and Table O data.
A focused Regents Chemistry answer on nuclear chemistry: the types of radiation and their symbols, balancing nuclear equations by conserving mass number and atomic number, half-life calculations, and the difference between fission and fusion.
Sources & how we know this
- Physical Setting/Chemistry Core Curriculum — New York State Education Department (2002)
- Reference Tables for Physical Setting/Chemistry, 2011 Edition — New York State Education Department (2011)