Ch 10Halogen Derivatives — Class 12 Chemistry, concept-first.

Every organic compound can ultimately be traced back to the hydrocarbon family, since hydrocarbons are the parent structures from which other classes are built.

Halogen derivatives of hydrocarbons are formed when one or more hydrogen atoms of an aliphatic or aromatic hydrocarbon are replaced by halogen atoms (F, Cl, Br or I).

Monohalogen compounds are classified further by the position of the halogen atom and the hybridisation state of the carbon it is bonded to.

Common names of alkyl halides are formed by naming the alkyl group followed by the halogen name used as an adjective ending in '-ide' -- for example methyl iodide or tert-butyl chloride.

The chapter groups the methods of making alkyl (and aryl) halides into five families, developed one at a time in sections 10.3.1-10.3.5: making an alkyl halide starting from the corresponding alcohol…

The hydroxyl group of an alcohol can be replaced by a halogen atom in three ways. (a) Using a halogen acid (HX): the conditions needed depend on both the alcohol's structure and the acid used, and the…

Alkyl halides can be built up from hydrocarbons instead of from alcohols. Direct free-radical halogenation of an alkane is not a practical way to make a specific alkyl halide, because it is unselectiv…

Alkyl iodides are conveniently prepared by treating an alkyl chloride or bromide with sodium iodide dissolved in methanol or acetone (R-Cl + NaI in acetone - R-I + NaCl-down-arrow); because sodium chl…

Aryl chlorides and bromides can be prepared by direct halogenation of benzene and its derivatives through electrophilic aromatic substitution.

The method most commonly used to prepare aryl halides in practice is not direct electrophilic halogenation of the ring (section 10.3.4) but Sandmeyer's reaction, which starts from an aromatic diazoniu…

The physical properties of alkyl halides differ considerably from those of the alkanes they are derived from, once a hydrogen is replaced by a halogen.

Every halogen (X = F, Cl, Br, I) is more electronegative than carbon, so the carbon atom carrying the halogen develops a partial positive charge (C-delta+) while the halogen carries a partial negative…

Boiling points of alkyl halides are considerably higher than those of the corresponding alkanes, because of the higher polarity and higher molecular mass that the halogen brings.

Although alkyl halides are moderately polar compounds (section 10.4.1), they are insoluble in water. This is because alkyl halides cannot form hydrogen bonds with water molecules, so the attraction be…

This section introduces optical isomerism using 2-chlorobutane, CH3-CHCl-CH2-CH3, as the running example.

A chiral molecule and its mirror image share the same structural formula and the same molecular formula -- they have exactly the same atoms bonded to exactly the same atoms -- but the spatial arrangem…

To understand optical activity (the next section), it is necessary first to understand plane polarised light.

When an aqueous solution of certain organic compounds -- such as sugar or lactic acid -- is placed in the path of plane polarised light, the light that emerges on the other side has its oscillations i…

Optical isomers that are non-superimposable mirror images of each other are called enantiomers (also called enantiomorphs or optical antipodes).

Two representations are used to show the configuration of a chiral carbon and the three-dimensional structure of an optical isomer on flat paper: the wedge formula and the Fischer projection formula (…

This section develops the chemical reactivity of halogen derivatives across seven sub-sections. It opens with a simple qualitative laboratory test that confirms the presence of halogen in an organic c…

Haloalkanes are of neutral character in aqueous medium -- they do not turn litmus, for instance. On warming a haloalkane with aqueous sodium or potassium hydroxide, the covalently bonded halogen atom…

When one group bonded to a carbon in a substrate is replaced by another group, with no change in the hybridisation state of that carbon, the reaction is called a substitution reaction.

Table 10.3's reactions show that, in a nucleophilic substitution of an alkyl halide, the halogen atom detaches from carbon and a new bond forms between that (electrophilic) carbon and the incoming nuc…

Whether a given alkyl halide reacts by SN1 or by SN2 is controlled by three independent factors. (a) Nature of the substrate: the SN2 transition state is pentacoordinate and therefore crowded (Fig.

When an alkyl halide that has at least one beta-hydrogen is boiled with an alcoholic solution of potassium hydroxide, it undergoes elimination of a hydrogen atom from the beta-carbon together with the…

Active metals such as sodium, magnesium and cadmium readily combine with alkyl chlorides, bromides and iodides to form compounds containing a carbon-metal bond, known as organometallic compounds.

Haloarenes react differently from haloalkanes in three distinct ways, covered here in turn. (a) Reaction with active metals: an aryl halide reacted together with an alkyl halide and sodium metal in dr…

This closing section surveys six specific, individually named polyhalogen compounds one at a time, covering for each both its practical uses (as a solvent, refrigerant, propellant, insecticide, antise…

Dichloromethane, also called methylene chloride (CH2Cl2), is a colourless, volatile liquid with a moderately sweet aroma.

Chloroform, also called trichloromethane (CHCl3), is a colourless liquid with a distinctive, peculiar sweet smell.

Carbon tetrachloride, also called tetrachloromethane (CCl4), is a colourless liquid with a sweet smell.

Iodoform, also called triiodomethane (CHI3), is a yellow crystalline substance with a disagreeable smell.

Freons are organic compounds of chlorine and fluorine -- chlorofluorocarbons, or CFCs -- and are commonly used as refrigerants.

Dichlorodiphenyltrichloroethane (DDT) is a colourless, tasteless and odourless crystalline compound with insecticidal properties.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

The end-of-chapter questions of this group, exactly as the book prints them.

Sample papers and previous-year board questions for this subject.