PharChem2_Module 7 Hydrocarbons.pdf

PHARMACEUTICAL ORGANIC CHEMISTRY MODULE 5: HYDROCARBONS HYDROCARBONS TYPES AND CLASSIFICATION S AT U R AT E D U N S AT U R AT E D CYCL O AL K ANE Contain o n l y single bonds a n d are heavily laden w i t h hydrogen. These c o m p o u n d s consist o f a single, d o u b l e o r triple bond between c...

PHARMACEUTICAL ORGANIC CHEMISTRY MODULE 5: HYDROCARBONS HYDROCARBONS TYPES AND CLASSIFICATION S AT U R AT E D U N S AT U R AT E D CYCL O AL K ANE Contain o n l y single bonds a n d are heavily laden w i t h hydrogen. These c o m p o u n d s consist o f a single, d o u b l e o r triple bond between carbonc a r b o n atoms. These hydr ocar bons possess one o r m ult iple c ar bon rings. The h yd r o g e n a t o m is at t ac hed t o t he c ar bon ring. TYPES OF HYDROCARBONS AL I P H AT I C AROM ATIC ALIPHATIC HYDROCARBON They ar e straight chain structures having n o rings in them. Can be classified f u r t h e r b y t h e t y p e of bonds t h e y contain. TYPES OF HYDROCARBONS AL I P H AT I C AROM ATIC AROMATIC HYDROCARBON Are circularly structured organic c o m p o u n d s t h a t contains s i g m a bonds a l o n g w i t h delocalized pi electrons. Less reactive t h a n alkanes, useful in industrial solvents f o r n o n p o l a r compounds PHYSICAL PROPERTIES H y d r o c a r b o n s ar e n o n p o l a r substances w i t h w e a k i n t e r m o l e c u l a r forces, l o w m e l t i n g a n d boiling t em per atures, a n d p o o r o r n o soluble in p o l a r solvents. ALIPHATIC HYDROCARBONS GASES Fewer than 5 carbons atoms LOW LIQUID SOLID 5-15 carbon atoms INTERMEDIATE More than 15 carbon atoms HIGH VOLATILITY Hydrocarbons, in general, are volatile because they can evaporate easily into the air. DENSITY Hydrocarbons are less dense than water BOILING POINT Higher boiling point (stronger van der waals) increase number of carbons/ longer chain Increase boiling point, increase molar mass LINEAR CHAIN Higher boiling point than branched BRANCHED CHAIN Increased symmetry leads to higher melting point and lower boiling point ALIPHATIC HYDROCARBONS ALKANE ALKENE ALKYNE -88 Celsius -103.7 Celsius -84 Celsius AROMATIC HYDROCARBONS BENZENE & WATER BENZENE SOOTY YELLOW FLAME Generally nonpolar and immiscible with water Often Unreactive, they are useful as solvents for other nonpolar compounds Characterized by a sooty yellow flame SOLUBILITY A r o m a t i c c o m p o u n d s are less dense t h a n w a t e r a l t h o u g h t h e y are usually m o r e dense t h a n other hydrocarbons Ha l o g e n a t e d benzene c o m p o u n d s are denser t h a n water. A r o m a t i c h yd r o c a r b o ns are insoluble in w a t e r a n d are used as solvents f o r o t h e r organic c o m p o u n d CHEMICAL PORPERTIES H yd r o c a r b o n s are n o n p o l a r organic compounds with weak intermolecul ar forces. The lack o f s t r o n g intermolecu lar a t t r a c tive forces influences their properties. CHEMICAL PROPERTIES LONDON DISPERSION FORCES The we a k London forces operating between alkane molecules begin to provide en o u g h i n te rmo l e cu l a r a ttra cti o n f o r these substances t o exist as liquids as their m o l e c u l a r size increases. DIFFERENT M O L E C U L AR S T R U C T U RE S H yd r o ca rb o n s have diffe rent empirical formulas. This is p r i ma ri l y due t o "self- bond i ng" or ca rb o n catenation, wh i ch prevents th e h yd r o c a r b o n f r o m being c o m p l e t e l y sa tu r a te d b y t h e f o r ma t i o n o f do u bl e o r triple bonds. SINGLE CARBON BOND Are said t o be s a t u r a t e d a n d less reactive MULTIPLE CARBON BOND Are said to be unsaturated and far more reactive ALIPHATIC CHEMICAL PROPERTIES Known as saturated hydrocarbons because they only have single bonds between carbon and hydrogen atoms. LESS REACTIVE ALKANE React with a much greater variety of compounds than alkanes. ALKENE Undergo substitution reactions, whereas alkenes and alkynes undergo addition reactions. MOST REACTIVE BROMINE REACTION Potassium permanganate is an oxidizing agent that reacts with unsaturated aliphatic hydrocarbons. Does not react with alkanes or aromatic hydrocarbons. AROMATIC CHEMICAL PROPERTIES Double bonds in aromatic compounds are less likely to participate in addition reactions than those found in typical alkenes. Composed of closed rings of delocalized electrons originating from alternative single and double bonds. Aromatic compounds with at least one conjugated ring of single and double bonds are extremely stable. Aromaticity (i.e., additional stability provided by resonance) is present AROMATIC CHEMICAL PROPERTIES Ratio of hydrogen atoms to carbon atoms is relatively high in these molecule types. When burned. Aromatic hydrocarbons having multiple bonds are unsaturated in nature BROMINE REACTION Decoloration of bromine is often used as a test for a carbon-carbon double bond. Alkenes react in the cold with pure liquid bromine, or with a solution of bromine in an organic solvent like tetrachloromethane. Cyclohexene reacts with bromine in the same way and under the same conditions as any other alkene. NITRATION OF BENZENE NITRATION REACTION A process wherein a nitro group is added in an organic compound. Positive result is yellow oily substance called Nitrobenzene Benzene will react with hot concentrated nitric acid to produce nitrobenzene A safer reaction involves a mixture of nitric and sulfuric NITRATION OF BENZENE The reaction mechanism is similar to an acid catalyzed dehydration. METHYL BENZOATE A methyl ester formed by the condensation of methanol & benzoic acid in the presence of strong acid. Nitrating Methyl Benzoate with HNO3 using H2SO4 as catalyst. Nitrating the Benzene ring is an electrophilic aromatic substitution reaction. REACTION OF HYDROCARBONS SUBSTITUTION R E AC T I O N Arenes undergo substitution reactions, in which the aromatic hydrogen is replaced with an electrophile, hence their reactions proceed via electrophilic substitution. ADDITION R E AC T I O N Addition reaction is restricted to only alkenes and alkynes. It also involves many reagents situated across pi bonds like chlorine, and water. COMBUSTION Hydrocarbon combustion is the chemical reaction in which a hydrocarbon reacts with oxygen to produce carbon dioxide, water, and heat. COMBUSTION COMBUSTION OF M E T H A N O L Involves a chemical reaction between methanol and oxygen. COMBUSTION OF P R O P AN E COMBUSTION OF ET HENE Widely employed in cooking setups like fire grills Ethene burns in the presence of oxygen to form carbon dioxide and water along with the evolution of heat and light.equation