【正文】 a reaction in which heat is releasedendothermic reaction: a reaction in which the enthalpy of the products is higher than that of the reactants。 the position of equilibrium for an exergonic reaction favors productsendergonic reaction: a reaction in which the Gibbs free energy of the products is higher than that of the reactants。 that is, to rotate one carbon by 90176。CThe reason of the relative rates of radical formation:By paring the values for the sum of the two propagating steps for the monohalogenation of methane, we can understand why alkanes undergo chlorination and bromination but not iodination and why fluorination is too violent a reaction to be useful.Chapter 3 Alkene Structure and nomenclatureSaturated hydrocarbons:. alkanes contain the maximum number of carbon–hydrogen bonds possible—that is, they are saturated with hydrogen.Unsaturated hydrocarbon: contains one or more carboncarbon double or triple bondsAlkene: contains a carboncarbon double bond and has the general formula CnH2n.Degree of unsaturation (or Index of hydrogen deficiency) :. The total number of πbonds and rings in an alkene is called its degree of unsaturation.Notes:the molecular formula of the reference hydrocarbon is CnH2n+2for each atom of a Group 7 element (F, Cl, Br, I), add one Hno correction is necessary for the addition of atoms of Group 6 elements (O,S) to the reference hydrocarbonfor each atom of a Group 5 element (N, P), subtract one hydrogenA double bond consists of one sigma bond formed by the overlap of sp2 hybrid orbitals and one pi bond formed by the overlap of parallel 2p orbitalsthe two carbon atoms of a double bond and the four atoms bonded to them lie in a plane, with bond angles of approximately 120176。torsional strain: there are 6 sets of eclipsed hydrogen interactionsstrain energy is about 116 kJ ( kcal)/mol Cyclobutanepuckering from planar cyclobutane reduces torsional strain but increases angle strainthe conformation of minimum energy is a puckered “butterfly” conformationstrain energy is about 110 kJ ( kcal)/mol Cyclopentanepuckering from planar cyclopentane reduces torsional strain, but increases angle stainthe conformation of minimum energy is a puckered “envelope” conformationstrain energy is about 42 kJ ( kcal)/mol CyclohexaneChair conformation: the most stable puckered conformation of a cyclohexane ringall bond CCC bond angles are 176。 given the symbol R1. Determine the number of carbons in the longest continuous carbon chain. This chain is called the parent hydrocarbon.2. The name of any alkyl substituent that hangs off the parent hydrocarbon is cited before the name of the parent hydrocarbon, together with a number to designate the carbon to which the alkyl substituent is attached.3. If more than one substituent is attached to the parent hydrocarbon, the chain is numbered in the direction that will result in the lowest possible number in the name of the pound.4. When both directions lead to the same lowest number for one of the substituents, the direction is chosen that gives the lowest possible number to one of the remaining substituents.5. If the same substituent numbers are obtained in both directions, the first group cited receives the lower number.6. If a pound has two or more chains of the same length, the parent hydrocarbon is the chain with the greatest number of substituents.7. Name the substituent the attached substituent. Nomenclature of Cycloalkanes Cycloalkanes are alkanes with their carbon atoms arranged in a ring.The rules for naming cycloalkanes resemble the rules for naming acyclic alkanes:1. Determine the parent. 2. Number the substituent: If the ring has two different substituents, they are cited in alphabetical order and the number 1 position is given to the substituent cited first.3. The substituent given the number 1 position is the one that results in a second substituent getting as low a number as possible. Nomenclature of BicycloalkanesBicycloalkane: an alkane that contains two rings that share two carbons Bicyclo[]decane Bicyclo[]nonane Bicyclo[]heptaneparent is the alkane of the same number of carbons as are in the ringsnumber from a bridgehead, along longest bridge back to the bridgehead, then along the next longest bridge, etc.show the lengths of bridges in brackets, from longest to shortest ConformationsConformation: any threedimensional arrangement of atoms in a molecule that results from rotation about a single bondNewman projection: a way to view a molecule by looking along a carboncarbon single bondStaggered conformation: a conformation about a carboncarbon single bond in which the atoms or groups on one carbon are as far apart as possible from the atoms or groups on an adjacent carbonEclipsed conformation: a conformation about a carboncarbon single bond in which the atoms or groups of atoms on one carbon are as close as possible to the atoms or groups of atoms on an adjacent carbonDihedral angle (Q): the angle created by two intersecting planesEthane as a function of dihedral angleconformations of butane as a function of dihedral angleCyclopropaneangle strain: the CCC bond angles are pressed from 176。carbonQuaternary (4176。 H: a hydrogen bonded to a 3176。 carbonTertiary (3176。) C: a carbon bonded to two other carbons2176。 H: a hydrogen bonded to a 1176。the unhybridized 2p orbitals are perpendicular to each other and to the line created by the axes of the two sp hybrid orbitalsBonding in Acetylene, C2H2Hybrid OrbitalsChapter 2 Alkane and cycloalkane Alkane The definition