chemistry

• lone pairs repel bonded pair closer together by 2.5 degrees as lone pairs take up more space closer to the atom and repel more strongly
• 2 electron pairs, linear shape with a bond angle of 180
• 3 electron pairs , trigonal planar , bond angle of 120
• 4 electron pairs, tetrahedral shape with a bond angle of 109.5
• 6 electron pairs, octahedral shape bond angle of 90
• Homolytic fisson , one electron from the shared pair goes to each bonded atom , forming radicals
• Heterolytic fission, the shared pair of electrons within a covalent bond goes entirely to one of the bonding atoms forming two ions , one positive and one negative
• electronegativity , the attraction between a bonded atom and shared pair of electrons
• electronegativity increases as you move up and right along the periodic table , due to increases in the nuclear charge and decrease in the atomic radius
• non polar bond , the electron pair is shared equally between bonded atoms due to similar electronegativity , such as within same atoms
• polar bond , the electron pair is shared unequally due to differences in electronegativity, causing the shared electrons to reside closer to the more electronegative atom , creating a dipole moment
• london forces, weak intermolecular forces which exist between all molecules , polar and non polar
• induced diopoles, the movement of electrons produces a changing dipole, called an induced dipole which is temporary, the induced dipole induces a dipole in neighbouring molecules and so on, these induced dipole attract one another
• The more electrons within a molecule, the stronger the instantaneous and induced dipole , the greater the induced dipole interactions and the stronger the attraction between molecules
• non polar simple molecular substances are held together by weak london forces, are soluble in non polar solvents rather than polar solvents as intermolecular forces form between the molecule and the non polar solvent causing the intermolecular forces within the simple molecular lattice to break down and dissolve
• in polar solvents there are little interactions between the polar solvents and molecule leading to low solubilities
• polar simple molecular substance can dissolve in polar solvents
• Hydrogen bonds, the permenant dipole dipole interactions between electronegative atoms and a hydrogen atom , the strongest type of intermolecular forces
• Hydrogen bonds hold water molecules apart in an open lattice structure , the water molecules are even further apart within ice
• solid ice is less dense than water as it floats
• The hydrogen bonds extend outwards holding water molecules slightly apart and forming an open tetrahedral lattice which is full of holes , at bond angles of 180 , the holes in the lattice decrease the density of the water on freezing
• Due to the presence of hydrogen bonds between molecules , water has a high boiling point
• trigonal bipyramidal, the electron pair , with lone pair , bond angle 107
• 104.5, bond angle of water #
• aldehydes can be oxidised to form carboxylic acids, ketones cannot be oxidised
• The carbon oxygen double bond in aldehydes and ketones is made up of a sigma and pie bond . oxygen is slightly more electronegative than carbon and therefore attracts nucleophiles, resulting in nuclepohilic addition
• Aldehydes and ketones can be reduced by NaBH4 to form alcohols, by being warmed with it in solution
• Aldehydes are reduced with nabh4 to form primary alchols
• ketones are reduced with Nabh4 to form secondary alchols
• Hydrogen cyanide adds across the c to o double bond in aldehydes and ketones to increase the length of the carbon chain to form an -oxynitrile
• bradys agent , 2,4 DNP, is used to detect the presence of carbonyls functional group , as it reacts with a carbonyl , it forms a yellow precipitate
• silver nitrat plus sodium hydroxide forms a brown precipitate, dilute ammonnia is then added to make the solution go colourless, this is now tollen's reagent which is used to test between aldehydes and ketones
• add tollen's reagent to an unknown solution and place in a water bath for 10-15 minutes, if a silver mirror is formed then an aldehyde is present
• carboxylic acids are soluble in water due to the presence of their oh , hydroxyl group which can form hydrogen bonds with water , however as the carbon chain length of the carboxylic acid increases, water solubility decreases
• carboxylic acids can undergo neutralisation reactions to form a carboxylate salt
• carboxylic acid derivatives are compounds that can be hydrolysised to form the parent carboxylic acid. derivatives contain an acyl group
• esters are derivatives of carboxylic acids , they end in -oate
• acyl chlorides are also derivatives of carboxylic acids , end in -oyl chloride
• acid anhydrides are two carboxylic acids joined together by the removal of a water molecule , ends in -oic anhydride
• Alcohols can react with a carboxylic acids to form a ester , the aldol is warmed slightly with the carboxylic acid and some sulfuric acid to form an ester and a water molecule