additive

(adjective)

A sculptural process in which the artist begins with little to no material and gradually attaches more material until the desired form is achieved.

Related Terms

Examples of additive in the following topics:

  • Addition Reactions

    • There are two main types of polar addition reactions: electrophilic addition and nucleophilic addition.
    • Two non-polar addition reactions also exist: free radical addition and cycloadditions.
    • In the related addition-elimination reaction, an addition reaction is followed by an elimination reaction; in most reactions, this involves addition to carbonyl compounds in nucleophilic acyl substitution.
    • Most addition reactions to alkenes follow the mechanism of electrophilic addition.
    • Top to bottom: electrophilic addition to alkene, nucleophilic addition of nucleophile to carbonyl, and free radical addition of halide to alkene.

  • ANOVA Assumptions

    • Kempthorne and his students make an assumption of unit-treatment additivity.
    • The assumption of unit-treatment additivity usually cannot be directly falsified; however, many consequences of unit-treatment additivity can be falsified.
    • For a randomized experiment, the assumption of unit-treatment additivity implies that the variance is constant for all treatments.
    • Therefore, by contraposition, a necessary condition for unit-treatment additivity is that the variance is constant.
    • List the assumptions made in a one-way ANOVA and understand the implications of unit-treatment additivity

  • Addition by Electrophilic Reagents

    • The reactions are even more exothermic than the additions to alkenes, and yet the rate of addition to alkynes is slower by a factor of 100 to 1000 than addition to equivalently substituted alkenes.
    • One problem, of course, is that the products of these additions are themselves substituted alkenes and can therefore undergo further addition.
    • Consequently, there is a delicate balance as to whether the product of an initial addition to an alkyne will suffer further addition to a saturated product.
    • After all, addition reactions to alkynes are generally more exothermic than additions to alkenes, and there would seem to be a higher π-electron density about the triple bond ( two π-bonds versus one ).
    • It is possible that vinyl cations stabilized by conjugation with an aryl substituent are intermediates in HX addition to alkynes of the type Ar-C≡C-R, but such intermediates are not formed in all alkyne addition reactions.

  • Properties of Aldehydes and Ketones

    • Thus, reversible addition of water to the carbonyl function is fast, whereas water addition to alkenes is immeasurably slow in the absence of a strong acid catalyst.
    • This suggests that addition reactions to carbonyl groups should be thermodynamically disfavored, as is the case for the addition of water.
    • All of this is summarized in the following diagram (ΔHº values are for the addition reaction).
    • Acids and bases catalyze both the addition and elimination of water.
    • This can only be explained by the addition-elimination mechanism shown here.

  • Additional Funds Needed (AFN)

    • AFN is "additional funds needed," and refers to the additional resources that will be needed for a company to expand its operations.
    • AFN stands for "additional funds needed. " It is a concept used most commonly in business looking to expand operations and influence.
    • AFN is a way of calculating how much new funding will be required, so that the firm can realistically look at whether or not they will be able to generate the additional funding and therefore be able to achieve the higher sales level.

  • Adding and Subtracting Vectors Graphically

    • Since vectors are graphical visualizations, addition and subtraction of vectors can be done graphically.
    • The graphical method of vector addition is also known as the head-to-tail method .
    • For vector addition it does not matter which vector you draw first since addition is commutative, but for subtraction ensure that the vector you draw first is the one you are subtracting from.
    • This video gets viewers started with vector addition and subtraction.
    • The first lesson shows graphical addition while the second video takes a more mathematical approach and shows vector addition by components.

  • Addition Reactions Initiated by Electrophilic Halogen

    • The stereoselectivity of these additions is strongly anti, as shown in many of the following examples.
    • On the other hand, if two chiral centers are formed in the addition the reaction will be diastereomer selective.
    • This is clearly shown by the addition of bromine to the isomeric 2-butenes.
    • Anti-addition to cis-2-butene gives the racemic product, whereas anti-addition to the trans-isomer gives the meso-diastereomer.
    • By adding AgOH, the concentration of HOCl can be greatly increased, and the chlorohydrin addition product obtained from alkenes.

  • Addition of Lewis Acids (Electrophilic Reagents)

    • The proton is not the only electrophilic species that initiates addition reactions to the double bond.
    • This undergoes successive intramolecular shifts of alkyl groups from boron to oxygen, accompanied in each event by additional peroxide addition to electron deficient boron.
    • Since the oxymercuration sequence gives the same hydration product as acid-catalyzed addition of water (see Brønsted acid addition), we might question why this two-step procedure is used at all.
    • The addition of borane, BH3, requires additional comment.
    • Also, all three hydrogens in borane are potentially reactive, so that the alkyl borane product from the first addition may serve as the hydroboration reagent for two additional alkene molecules.

  • Stereoselectivity in Addition Reactions to Double Bonds

    • We see then that addition reactions to this function might occur in three different ways, depending on the relative orientation of the atoms or groups that add to the carbons of the double bond: (i) they may bond from the same side, (ii) they may bond from opposite sides, or (iii) they may bond randomly from both sides.
    • The first two possibilities are examples of stereoselectivity, the first being termed syn-addition, and the second anti-addition.
    • If the two-step mechanism described above is correct, and if the carbocation intermediate is sufficiently long-lived to freely-rotate about the sigma-bond component of the original double bond, we would expect to find random or non-stereoselective addition in the products.
    • The interesting differences in stereoselectivity noted here provide further insight into the mechanisms of these addition reactions.

  • The Addition Rule

    • The addition rule states the probability of two events is the sum of the probability that either will happen minus the probability that both will happen.
    • The addition law of probability (aka addition rule or sum rule), states that the probability that $A$ or $B$ will happen is the sum of the probabilities that $A$ will happen and that $B$ will happen, minus the probability that both $A$ and $B$ will happen.
    • The addition rule is summarized by the equation $P(A \cup B) = P(A)+P(B)-P(A \cap B)$.
    • Then the addition law simplifies to: