Hydrocarbon is a compound consisting of hydrogen and carbon only Molecular formula: The formula which shows the actual number of each type of atom Saturated: Contain single carbon-carbon bonds only Unsaturated : Contains a C=C double bond General formula: algebraic formula for a homologous series e.g. CnH2n Empirical formula: shows the simplest whole number ratio of atoms of each element in the compound 4.1.1 Organic: Basic Concepts Basic definitions to know Displayed formula: show all the covalent bonds present in a molecule When drawing organic compounds add the hydrogen atoms so that H each carbon has 4 bonds C C C H H H H H H C C H H H H H Drawing Displayed formulae Remember that the shape around the carbon atom in saturated hydrocarbons is tetrahedral and the bond angle is 109.5o C C H H H H H H N Goalby chemrevise.org 1 Skeletal formula shows the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional Groups. Structural formula shows the minimal detail that shows the arrangement of atoms in a molecule, eg for butane: CH3CH2CH2CH3 or CH3 (CH2 )2CH3 , OH 2-methylbutane But-2-ene Butan-1-ol cyclohexane cyclohexene Aliphatic: a compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings Alicyclic : an aliphatic compound arranged in non-aromatic rings with or without side chains Aromatic : a compound containing a benzene ring Saturated: single carbon–carbon bonds only Unsaturated : The presence of multiple carbon–carbon bonds, including C=C, C≡C and aromatic rings N Goalby chemrevise.org 2 Homologous series are families of organic compounds with the same functional group and same general formula. •They show a gradual change in physical properties (e.g. boiling point). • Each member differs by CH2 from the last. • same chemical properties. Functional group is an atom or group of atoms which when present in different molecules causes them to have similar chemical properties
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4.1.1 Basic concepts of organic chemistry
(b) interpretation and use of the terms: (i) general formula (the simplest algebraic formula of a member of a homologous series) e.g. for an alkane: CnH2n+2 (ii) structural formula (the minimal detail that shows the arrangement of atoms in a molecule) e.g. for butane: CH3CH2CH2CH3 or CH3(CH2) 2CH3 (iii) displayed formula (the relative positioning of atoms and the bonds between them) e.g. for ethanol: H C H H C H H O H (iv) skeletal formula (the simplified organic formula, shown by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups) e.g. for butan-2-ol: OH M4.2 See also 2.1.3 b for empirical formula and molecular formula. Definitions not required. In structural formulae, the carboxyl group will be represented as COOH and the ester group as COO. The symbols below will be used for cyclohexane and benzene: HSW8 Communication using organic chemical structures; selecting the appropriate type of formula for the context. Functional groups (c) interpretation and use of the terms: (i) homologous series (a series of organic compounds having the same functional group but with each successive member differing by CH2) (ii) functional group (a group of atoms responsible for the characteristic reactions of a compound) (iii) alkyl group (of formula CnH2n+1) (iv) aliphatic (a compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings) (v) alicyclic (an aliphatic compound arranged in non-aromatic rings with or without side chains) (vi) aromatic (a compound containing a benzene ring) (vii) saturated (single carbon–carbon bonds only) and unsaturated (the presence of multiple carbon–carbon bonds, including C=C, C C / and aromatic rings) Definition required for homologous series only. R may be used to represent alkyl groups, but also other fragments of organic compounds not involved in reactions. The terms saturated and unsaturated will be used to indicate the presence of multiple carbon–carbon bonds as distinct from the wider term ‘degree of saturation’ used also for any multiple bonds and cyclic compounds. (d) use of the general formula of a homologous series to predict the formula of any member of the series
4.1.1 basic concepts and hydrocarbons Page 1 - 2
Oxford Textbook Pages : 172 - 173, 179 - 181
CGP Revision Guide Pages : 84 - 85