lecture-3 updated all about hydrocarbons.pptx

All about hydrocarbons

1. H Y DR O C A R B O N S & THE I R F UNC T IO N A L GROUPS Saliha salam (Lecturer)

2. Hydrocarbons Hydrocarbons are organic compounds that are entirely made up of only two kinds of atoms – carbon and hydrogen . Typicaly, hydrocarbons are colorless gases that have very weak odors. Hydrocarbons can feature simple or relatively complex structures and can be generally classified into four subcategories, namely alkanes, alkenes, alkynes, and aromatic hydrocarbons. Furthermore, hydrocarbons such as propane and butane are used for commercial fuel purposes in the form of Liquefied Petroleum Gas(LPG). Benzene, one of the simplest aromatic hydrocarbons, serves as raw material for the synthesis of many synthetic drugs.

3. The molecular formula for these compounds is C x H y . The existence of hydrocarbons is seen in plants and trees. For example, Carotenes is an organic pigment that is found in green l ea v e s an d c a rr o t s . These hydrocarbons make up 98% of natural crude rubber.

4. Fun c t i o n s o f h y d r o c a r bon s Hydrocarbons are the principal constituents of petroleum and natural gas. They serve as fuels and lubricants as well as raw materials for the production of plastics, fibers, rubbers, solvents, explosives, and industrial chemicals.

5. C la ss ifi c at i o n an d T y p e s o f Hy d r o c a r bo n s ba s e d o n The i r Structures

6. T y p e s o f H y dr o c arbo n s 1 ) S aturate d H ydrocarbo n In these compounds, carbon-carbon atoms and carbon-hydrogen atoms are held together by single bonds. These single-bonded compounds are the simplest hydrocarbons. The s e t y pe s o f h y d r o c a r b o n s don’ t ha v e doub l e o r tr ipl e bond s . Th e y a r e t o g e t he r c a lle d al k ane s w hi c h h a v e a g e n e r a l f o rm ul a C n H 2n +2

7.  Draw the skeletal and expended structures for th e s e t w o mo l e c u l e s

8. Solution Each carbon atom is converted into the end of a line or the place where lines intersect. Al l h y d r o ge n a t o m s a t t a c he d t o t h e c a r bo n a t o m s a r e le f t ou t o f t h e structure (although we still need to recognize they are there)

9. Solution

10. P ropert i e s o f Al k ane s Greater numbers of atoms in the molecules will lead to stronger intermolecular attractions (dispersion forces) and correspondingly different physical properties of the molecules. Properties such as melting point and boiling point (Table 1) usually change smoothly and predictably as the number of carbon and hydrogen atoms in the molecules change.

11. Hydrocarbons with the same formula, including alkanes, can have different structures. For example, two alkanes have the formula C 4 H 10 Th e y a r e c alle d n - b u t a n e a n d 2 - m e t h y lp ro p a n e ( o r i s o b u t a n e ) , a n d hav e t h e f o ll o wi n g L e wi s s tr u c t u r e s .

12. 2 ) U ns at ura t e d H ydrocarbons : These compounds consist of a single, double or triple bond between carbon- carbon atoms. The double-bonded compounds are called alkenes and the triple bonded compounds are called alkynes . The general formula for alkenes is C n H 2n and for alkynes the general formula is C n H 2n-2 . carbon atoms linked by a double bond are bound together by two bonds, one σbond, and one πbond. Double and triple bonds give rise to a different geometry around the carbon atom that participates in them, leading to important differences in molecular shape and properties .

13. E x a m p l e o f Alk en e Ethene, C 2 H 4 , is the simplest alkene. Each carbon atom in ethene, commonly called ethylene, has a trigonal planar structure. The second member of the series is propene (propylene), the butene i s o m e r s f ollo w i n t h e s e r ie s . Four carbon atoms in the chain of butene allow for the formation of isomers based on the position of the double bond, as well as a new form of isomerism.

14. E x a m p l e o f A lk y n e Hydrocarbon molecules with one or more triple bonds are called alkynes; they make up another series of unsaturated hydrocarbons. Twocarbon atoms joined by a triple bond are bound together by one σbond and two πbonds. The simplest member of the alkyne series is ethyne, C 2 H 2 , commonly called acetylene. Th e Le w i s s tr u c t u r e f o r e t h y ne , a lin e a r m o l e c ul e , i s :

15. P ropert i e s o f A lky n e s In general, alkynes are in gaseous form and they are soluble in organic solvents, like benzene and acetone. They are, however, insoluble in water. I n gene r a l , al ky n e s ar e m or e a c i d i c t h a n a lk e n e s an d alka n e s . The boiling point of alkynes also tends to be slightly higher than alkenes an d a l k ane s .

16. A ro m a t i c H y dr o c arbo n s o r A ren e s B e n z e n e , C 6 H 6 , i s t h e s i m ple s t m e m be r o f a la r g e f a m il y of h y d r o c a r b o n s , c alle d a r o m a t i c h y d r o c a r b o n s .

17. U s e s o f H y dr o c arbo n s H y d r o c a r bon s a r e widel y u s e d a s f uel s . Fo r e x a m pl e L P G ( lique f ie d pe tr oleu m ga s ) , CN G( Liq u e f i e d na t u r a l ga s ) . Theyare used in the manufacturing of polymers such as polyethylene, polystyrene etc. These organic compounds find their application in the manufacturing of drugs and dyes as a starting material. Theyserve as lubricating oil and grease.

18. F un c t i ona l g r ou p s

19. Fun c t i on a l G roup s A functional group is defined as an atom or group of atoms within a molecule that has similar chemical properties whenever it appears in various compounds .

20. A lk en e s an d A lky n e s Al k e n e s a r e h y d r o c a r bo n s that c on t a i n on e o r m o r e doub l e bond s between neighboring carbon atoms. A l ky ne s c on t ai n on e o r m o r e t r ipl e bond s be t wee n ne i ghbo r i n g carbon atoms. Alkenes (left)contain one or more double bonds while alkynes (right) contain one or mo r e t r ip l e b o nd s .

21. A lc oho l Alcohol is a functional group that you probably are familiar with. In organic chemistry, the term alcohol refers to a compound containing the OH (hydroxy) group. Depending on the position of the OH group, alcohols can also be categorized as primary (1°), secondary (2°) or tertiary (3°).

22. E t her Ethers are a class of organic compounds characterized by an oxygen a t o m c onne ct e d t o t w o a l ky l o r a r y l g r oup s . An ether group is an oxygen atom connected to two alkyl or aryl groups. They follow the general formula R-O-R’. The C-O-C linkage is c ha r a ct e r i z e d b y bon d angle s o f 104 . 5 deg r ee s

23. K etone s ketones is a class of organic compounds that contain a carbonyl (C=O) group. Wh e n a c a r bo n y l f u n c t i ona l g r ou p i s p l a c e d wi t h i n a m o l e c u le , i t i s known as a ketone.

24. Aldehydes An aldehyde is an organic compound that contains a carbonyl group with the central carbon bonded to a hydrogen and R group (R- CHO).

25. C a r bo x yl i c Aci d s A carboxyl group (COOH) is a functional group consisting of a carbonyl group (C=O) with a hydroxyl group (O-H) attached to the same carbon atom. Carboxyl groups have the formula (-C=O)OH, usually written as -COOH or CO 2 H.

26. E s t er Esters are functional groups produced from the condensation of alcohol with a carboxylic acid and are named based on these components. Esters are an important functional group in organic chemistry, and they are generally written RCOOR’orRCO2R’.

27. A mi ne s Amines are compounds characterized by the presence of a nitrogen atom, a lone pair of electrons, and three substituents.

28. T ha n k Y o u

29. H O M E T AS K # 2 W r i te e q ua t i on s f o r t h e f o rm a t ion s o f al k e n e , al k an es , ald e h y d e s , k e t one s , a c id s , e st e rs , a m ine s , an d a m ide s .