Naming Organic Molecules

Transcription

1 Naming rganic Moecues Besides understanding the ester formation reaction, the naming of organic moecues is another important esson. Naming organic moecues is actuay rather invoved. We are just going to touch on the basics. In short, it s a about prefixes and fancy endings. The prefixes te you how many carbons there are. The most common prefixes are in the tabe beow. The endings te you the type of organic chemica. We are just going to focus on 11 of the many types. 1. Akanes - ydrocarbons (containing ony C & ) that contain NLY singe bonds. -Name of akanes aways end in -ane. Ex: prefix + ane EX: Propane - Just a certain # of carbons (as specified by prefix) with s making a of the carbons happy! Remember, there can ony be singe bonds and carbon can ony make four tota bonds per carbon. 1. Prop- means TREE CARBNS. Draw out your carbon chain... C -- C C 2. Knowing that carbon aways wants to make FUR bonds, make a of the carbons happy by fiing in s. RGANIC PREFIXES Meth- Eth- Prop- But- Pent- ex - ept- ct - Non- Dec- = # of Carbons one two three four five six seven eight nine ten C C C = C38 or C3C2C3 3. Write the formua from your drawing. - If you don t ike drawing your akanes out, their formua is represented by the foowing equation: Cn2n+2 - EX: methane C4, ethane C26, propane C38 2. Akenes- ydrocarbons that contains at east one doube bond - Name of akene aways ends in -ene. Ex: prefix + ene - A certain # of carbons (as specified by prefix) with one doube bond. The doube bond coud be between any two carbons in the moecue, but for our purposes - aways put the doube bond between the first two carbons. - You can draw the structure out or just know that the formua for an akene is represented by Cn2n

2 - EX: ethene or ethyene (same thing) = C24 \ / C = C -propene or propyene (same thing) = C36 / \ \ / C = C C R C C = C / \ 3. Akynes- ydrocarbons that contains at east one tripe bond - Name of akynes aways end in -yne. Ex: prefix + yne - A certain # of carbons (as specified by prefix) with one tripe bond. The tripe bond coud be between any two carbons in the chemica, but for our purposes, aways put the tripe bond between the first two carbons. - You can draw the structure out or just know that formua is represented by: Cn2n-2 EX: ethyne = C22 C C C C C propyne = C34 FUNCTINAL GRUPS: * 4. Acohos- rganic compounds in which a hydrogen has been repaced with an - group. - Genera format: R --, where R is a carbon chain. - Name of acohos aways ends in -ano. Ex: prefix + ano - To get the formuas, it is often very hepfu to draw out the structure. EX: Butano 1. But- means the acoho comes from butane and has FUR carbons. C C C C 2. repace an w/ group C C C C butane butano 3. Write the formua from the picture. Butano = C49 or C3C2C2C2 - EX: methano = C3, ethano = C25, propano = C35 * 5. rganic Acids or Carboxyic acids - rganic compounds that contains a carboxy group...c. - Genera format R-C R C

3 The from the carboxy group is actuay acidic (meaning it can dissociate in water to make +). owever, a organic acids are WEAK acids. Names of organic acids aways end in -anoic acid. EX: prefix + anoic acid owever, many organic acids are more often named via common names that don t foow this convention! Doh! To get the formuas, it is often hepfu to draw out the structure EX: Ethanoic Acid 1. Eth means TW carbons. C C 2. ne of the C s wi have a carbony group. C C 3. Make a of the remaining C s happy with s. C C 4. Write the formua. Ethanoic Acid (or ACETIC ACID) = C3C ** Pease notice that the common name for ethanoic acid is acetic acid!!! - EX: methanoic acid (formic acid) = C, butanoic acid (butyric acid) = C37C C C C C C 6. Esters: - For us, an ester is made when an acoho and carboxyic acid react. You wi see this in the introduction of the Ester s Lab. The genera format of an ester is...r C R {from acid} {from acoho} - Name esters by considering the acid and the acoho that reacted to make the ester in question. Name the acoho first - then the acid. For the acoho, change the ending to -y and for the acid, change the ending from ic to ate. This naming convention can be used on the systemic name or common name that is given to you for the acid or acoho. EX: (acoho)-y (acid)-ate prefix prefix EX: propano + ethanoic acid = propy ethanoate (remember the common name for ethanoic acid is acetic acid) So it can aso be... propano + acetic acid = propy acetate prefix prefi EX: methano + butanoic acid = methy butanoate (remember the common name for butanoic acid is butyric acid) So it can aso be... methano + butyric acid = methy butyrate

4 The remaining functiona groups are important to recognize but not so important to name Adehydes: - An adehyde contains a C= (carbony group) connected to at east 1 hydrogen atom. R C 8. Ketones - A ketone is simiar to an adehyde in that it aso contains a C= (carbony group), but in a ketone the carbon in the carbony group is not connected to any hydrogen atoms. R C R 9. Ethers - In an ether, an oxygen atom serves as a ink in a hydrocarbon chain. R R 10. Amines - In an amine, a hydrogen atom has been repaced by an amino group (N2). R N2 11. aides - aides are organic compounds in which one of more hydrogen have been R X repaced with a haide (X = F, C, Br, or I) Ex: C3C = choromethane, C3C2C = choroethane C C C C C NUMBERING CMPUNDS / Ex : Consider the foowing two compounds, C C C - C vs C C C C Both compounds woud be caed butano, but these compounds are different. In the first moecue, the is based off of the first carbon. In the second moecue, the is based off of the second carbon. ow can we name these compounds in such a way that the ocation of the - group is somehow indicated? Foow the foowing steps Determine the ongest possibe carbon chain in the moecue. This is the parent chain. 2. Next, identify anything coming off the parent chain. 3. Number the carbons in the parent chain so that the thing(s) coming off the chain can have the smaest possibe numbers. As an exampe, butano woud be numbered... C2 C2 C2 C where the - is coming off the #1 carbon as opposed to numbering it ike this.... C3 C2 C2 C where the - is coming off of the #4 carbon. 4. The number that the extension is coming off of is incorporated into the name: ex: C3 C C2 C3 2-butano ex: C2 C2 C2 C3 1-butano

5 C3 ex: C3 C C2 C3 2-methy butane C2C3 ex: C3 C2 C C2 C3 3-ethy pentane ex: C C C2 C2 C2 C3 1-hexyne ex: C3 C C C2 C2 C3 2 - hexyne ISMERS: There are many times of isomers but for our case, we our ony concerned with structura isomers. Structura isomers have the exact same formua, but different organization. The foowing three moecues are isomers: C3 C3 C2 C2 C2 C3 = pentane (C512) C3 C C3 = (C512) 2,2-dimethypropane C3 C3 C3 C C2 C3 = 2-methy butane (C512) IN SUMMARY... TYPE FRMULA DESCRIPTIN EXAMPLES Cn2n+2 - a singe bonds, C4 = methane, Akane ony C & C26 = ethane Cn2n - at east 1 doube bond C24 = ethene, Akene C36 = propene Cn2n-2 1- at east tripe bond C22 = ethyne, Akyne C34 = propyne Acohos R - has a hydroxy group C3 = methano, C25 = ethano rganic Acids (Carboxyic Acids) - has a carboxy group (-C) R C C3C, ethanoic acid Esters - an acid + an acoho methy ethanoate (methy acetate) R C R Adehydes - ends in R C - has an carbony group C3C2C, propana Ketone - has a carbony group- - has an R group on both sides R C R C3CC3, propanone Ether R R - sandwiched btwn two R s C3 C2C3, methoxyethane C3C2C2 N2, Amine R N2 - has a -N2 group aide R X X = F, C, Br, or I propanamine C Br

6 BREAK ASSIGNMENT: RGANIC CEMISTRY REVIEW QUESTINS 1. In a future ab you wi synthesize aspirin from saicyic acid and acetic anhydride. This reaction does not go to competion (there are some eftover reactants mixed with the products). Do some research and describe the method that woud be best used to separate your product from the excess reagents. Make sure to expain the chemistry behind this method. 2. What do the foowing prefixes stand for? a. meth- b. hex- c. prop- d. but- 3. a) Describe the differences between an adehyde and a ketone. b) Describe the difference between an organic acid and a ester. c) Which do you think woud be more soube in water, an organic acid or an ester. Assume both moecues to have the same R groups. Expain your reasoning. d) Which do you think woud be more soube in water, an ether or an acoho. Assume both moecues to have the same R groups. Expain your reasoning.

7 4. a) Identify the foowing compounds according to their functiona groups. Your choices of answers are isted beow. Akane Akene Akyne Acoho Adehyde rganic acid Ester Ether Amine aide Ketone b) Circe the part of the compound that is the functiona group 1. C3C2C2CC 2. C3C2C 3. C3C2 N2 4. C3C2C _ 5. C3C2 C3 6. C3C=CC3 C3 C3 7. C3 C 8. C3 C C2 C3 C3 C3 5. Name the foowing compounds: a. C3C2C2C2C3 b. C3C2CC2C3 c. C3C2 C d. C3C2C C2C3 C2C3 e. C3 CC f. C3CC2C2C3 _ C3 C2C3 C \ / g. C = C h. C3CC2C3 / \ _

8 i. C3C2C2C3 j. C3C2 k. C3C2C2C. C3Br 6. From the name, draw out the structure. a. cycohexane b. 2,2-dimethypentane c. 2-octano d. pentanoic acid e. dichoromethane f. 2-butene g. ethyne (acetyene) h. propy propanoate 7. Draw as many structura isomers as you can for the foowing compound. C3-C2--C2-C3 (h yes, you shoud aso name them!)